JXB Advance Access originally published online on November 29, 2004
Journal of Experimental Botany 2005 56(411):347-356; doi:10.1093/jxb/eri041
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESEARCH PAPER |
Dynamics of photosystem II: a proteomic approach to thylakoid protein complexes
Department of Biology, University of Turku, FIN-20014 Turku, Finland
* To whom correspondence should be addressed. Fax: +358 2 3335549. E-mail: evaaro{at}utu.fi
Received 7 April 2004; Accepted 27 September 2004
 |
Abstract |
|---|
 Top Abstract Light-induced damage to PSII...Heterogeneity of the PSII...Photoactivation of PSII and...Role of PSII protein...References |
|---|
Oxygenic photosynthesis produces various radicals and active oxygen species with harmful effects on photosystem II (PSII). Such photodamage occurs at all light intensities. Damaged PSII centres, however, do not usually accumulate in the thylakoid membrane due to a rapid and efficient repair mechanism. The excellent design of PSII gives protection to most of the protein components and the damage is most often targeted only to the reaction centre D1 protein. Repair of PSII via turnover of the damaged protein subunits is a complex process involving (i) highly regulated reversible phosphorylation of several PSII core subunits, (ii) monomerization and migration of the PSII core from the grana to the stroma lamellae, (iii) partial disassembly of the PSII core monomer, (iv) highly specific proteolysis of the damaged proteins, and finally (v) a multi-step replacement of the damaged proteins with de novo synthesized copies followed by (vi) the reassembly, dimerization, and photoactivation of the PSII complexes. These processes will shortly be reviewed paying particular attention to the damage, turnover, and assembly of the PSII complex in grana and stroma thylakoids during the photoinhibition–repair cycle of PSII. Moreover, a two-dimensional Blue-native gel map of thylakoid membrane protein complexes, and their modification in the grana and stroma lamellae during a high-light treatment, is presented.
Key words: Arabidopsis thylakoid membrane proteome, assembly of photosystem II, D1 protein, light stress, photosystem II photoinhibition, repair of photosystem II
|
Light-induced damage to PSII proteins |
|---|
|
TopAbstractLight-induced damage to PSII...Heterogeneity of the PSII...Photoactivation of PSII and...Role of PSII protein...References |
|---|
Photosynthetic water splitting involves highly oxidative chemistry, which is accomplished by a unique PSII complex. PSII converts light energy into chemical form using water as a source of electrons and liberating molecular oxygen as a side product. Light is a harmful substrate for the water-splitting PSII complex, exposing its protein subunits to structural damage. A number of protective systems have evolved in the thylakoid membrane and surrounding stroma to dissipate excess light energy and to scavenge various radicals and active oxygen species (Muller et al., 2001
; Ivanov and Khorobrykh, 2003), but there is always inherent inactivation and damage occurring in PSII with a very low quantum yield (Tyystjärvi and Aro, 1996; Anderson et al., 1997). Although oxidative damage occurs in PSII even at low light intensities, irreversible damage become evident in vivo in intact leaves only at high light intensities when the repair of PSII cannot keep pace with the constant oxidative damage (Aro et al., 1993).
It has been known for a long time that the PSII reaction centre D1 protein, which exhibits the highest turnover rate of all the thylakoid proteins (Mattoo et al., 1984), is the major target of oxidative damage in PSII (for reviews see Prasil et al., 1992; Aro et al., 1993). There is an extensive literature published on the mechanisms of PSII photoinactivation and damage to the D1 protein both under in vivo and in vitro conditions (for a review see Melis, 1999), and therefore these mechanisms will not be considered in detail here. However, it seems that the D1 protein is not the only target of photodamage in PSII. Several studies have suggested that the D2 protein also occasionally becomes damaged in light (Schuster et al., 1988; Jansen et al., 1996). More recently, one of the small PSII subunits, the PsbH protein, was also shown to be frequently replaced in PSII (Bergantino et al., 2003; E-M Aro et al., unpublished results). It is thus conceivable that the PsbH and D2 proteins, located in close proximity to the D1 protein (Zouni et al., 2001), occasionally become targeted for damage and degradation during the photoinhibition-repair cycle of PSII.
|
Heterogeneity of the PSII complexes: role in PSII photoinhibition-repair cycle |
|---|
|
TopAbstractLight-induced damage to PSII...Heterogeneity of the PSII...Photoactivation of PSII and...Role of PSII protein...References |
|---|
The different phases of the PSII photoinhibition-repair cycle of illuminated leaves have been addressed by first separating the membrane protein complexes of isolated thylakoids with Blue-native gel electrophoresis (BN-PAGE), followed by the separation of distinct protein subunits with denaturating SDS–PAGE. After silver staining, the protein subunits were identified with mass spectrometry (MALDI-TOF). A distinct feature of the thylakoid protein complexes is the diversity of the PSII complexes, as depicted for Arabidopsis thaliana (L.) Heynh. in Fig. 1. Table 1 gives an assignment for individual protein subunits for the recognition of respective protein complexes. In general, it was found that the BN-SDS-PAGE gel pattern of thylakoid proteins was very similar between different dicot species (Arabidopsis, pumpkin, spinach, tobacco) (Fig. 1; Suorsa et al., 2004
; Heinemeyer et al., 2004; E-M Aro et al., unpublished results). The smallest PSII subassembly visible in the silver-stained gel is the CP43-less PSII monomer which is composed of the D1/D2/CP47 proteins, the cytochrome (Cyt) b559 subunits (PsbE and PsbF), and the PsbI protein (of these small PSII subunits only PsbE is faintly seen in the silver-stained gel). The intact PSII monomer is the second biggest PSII complex and also has the CP43 internal antenna protein assembled (Fig. 1). The PSII dimer can be distinguished as a larger complex of c. 600 kDa, migrating in the BN-gel in close proximity to the PSI complex. PSII supercomplexes of increasing size then show the association of the LHCII antenna in varying combinations of the Lhcb1–6 proteins (Heinemeyer et al., 2004). ATP synthase, the cytochrome (Cyt) b6f dimer complex, and various free Lhcb1-6 protein assemblies can also be distinguished in Fig. 1. It is worth noting that the gentle solubilization of thylakoid membranes with n-dodecyl-ß-D-maltoside, used for thylakoids in Fig. 1, preferentially released the complexes from stroma thylakoids and those from grana appressions remained to larger extent unsolubilized.
|
|
For a more detailed understanding of the distribution of the various forms of PSII complexes in the thylakoid membrane, the thylakoids were fractionated into the grana and stroma membranes (Baena-Gonzalez et al., 1999
; Kyle et al., 1984) and the protein complexes were analysed from both fractions, with results depicted in Fig. 2. Grana membranes were strongly enriched in PSII dimers and PSII-LHCII supercomplexes, whereas only a small amount of PSII core monomers were present and the CP43-less PSII monomers were completely missing from the grana appressions. In addition to the PSII complexes, the monomeric and dimeric Cyt b6f complex, various free subassemblies of LHCII (Lhcb1–6 proteins) complexes, and traces of PSI complexes were present in the grana fraction. In stroma thylakoids, on the other hand, the PSII complexes as well as the various free LHCII subassemblies were present only as a minority, while the PSI complexes and ATP synthase were the dominating membrane protein complexes. The Cyt b6f complex was also present as a dimer. The PSII complex in stroma thylakoids was present mainly as a core monomer, and, in addition, traces of the CP43-less monomer were present in stroma thylakoids. PSII complexes in grana and stroma thylakoids also show functional heterogeneity and have been assigned a distinct role in the photoinhibition-repair cycle of the complexes (Guenther and Melis, 1990; Melis, 1999).
|
Damage occurs to PSII dimers and supercomplexes in the grana
Functional forms of PSII are located in the grana membranes where, most probably, oxidative damage also occurs, and so the PSII core dimers and supercomplexes are predominantly involved. Two-hour high-light illumination of pumpkin leaves (1500 µmol photons m–2 s–1), despite inducing approximately 30% inhibition of the photochemical efficiency of PSII (Fv/Fm), did not noticeably affect the distribution of the protein complexes in the grana and stroma membrane regions (thylakoid fractions only from high-light illuminated leaves are shown in Fig. 2). When the high-light illumination of leaves was performed in the presence of the chloroplast protein translation inhibitor lincomycin to block the repair process, no disassembly of the PSII complexes was observed in grana appressions (Fig. 2) despite nearly 60% photoinhibition and photodamage of the PSII centres (data not shown). Under severe photoinhibition, the integrity of photodamaged PSII complexes in the grana regions is apparently guaranteed by phosphorylation of the D1, D2, and CP43 proteins (Baena-Gonzalez et al., 1999
; see last section). This phosphorylation is likely to prevent a complete disassembly and a collapse of the photodamaged PSII complex in the grana region before migration to the repair site in non-appressed membranes.
Monomerization of PSII complexes is a prerequisite for repair in stroma thylakoids
In plant chloroplasts, the damaged PSII complex must exit the grana membrane, as the PSII complexes undergoing repair have definitively been localized to the stroma thylakoids where the ribosomes have access. Migration of the damaged PSII to stroma-exposed thylakoids can be regarded as the first step in the PSII repair cycle (Guenther and Melis, 1990; Melis, 1999). The mechanism and the exact site for PSII monomerization in the thylakoid membrane, upon photodamage in the grana or during an early repair phase in the stroma thylakoid, have been difficult to assess. The reversible mononer–dimer organization of PSII in the photoinhibition repair cycle has been more straightforward to assess in studies of cyanobacterial thylakoid membranes without any lateral heterogeneity. Recently, it was demonstrated that high-light illumination and damage to PSII severely reduced the content of PSII dimers and, conversely, increased the monomer forms of PSII in Synechocystis thylakoid membranes (Sakurai et al., 2003). Upon recovery from photoinhibition, the PSII dimers again became the dominating form in the thylakoid membrane. It is of interest to note here that the phosphatidylglycerol class of membrane lipids was shown to be particularly important for the dimer organization of PSII (Sakurai et al., 2003).
In higher plant chloroplasts, the blocking of the repair process of PSII by lincomycin, an inhibitor of protein synthesis in chloroplasts, resulted in a complete disappearance of the PSII core monomer complexes from the stroma membrane region (illumination of leaves in the presence of lincomycin, Fig. 2). Thus, in the absence of de novo synthesis and replacement of the damaged proteins in PSII, the entire PSII core monomer complex collapses upon degradation of the damaged D1 protein. This was accompanied by the accumulation of free CP47 and, to a minor extent, of free CP43 in the stroma-exposed thylakoid membranes (Fig. 2), whereas the other PSII protein subunits were not found free and were apparently subject to a more efficient proteolytic degradation than CP47.
Both the degradation of the damaged PSII protein subunits and their replacement by de novo synthesized ones take place on stroma thylakoids. This process requires at least a partial disassembly of the PSII complex. Although most often only the D1 protein is the target for photodamage, the D2 protein and the PsbH protein are also occasionally subject to irreversible damage. Considering the 3D structure of PSII (Ferreira et al., 2004; Zouni et al., 2001) and the experimental evidence collected so far, it is reasonable to conclude that at least the CP43 antenna protein, together with some as yet unidentified low molecular weight (LMW) subunits, are released from the PSII core monomer complex in the stroma-exposed thylakoid regions to allow the degradation of the damaged D1 protein. The CP43-less PSII monomers present in stroma thylakoid regions (Fig. 2) are probably an indication of this repair phase. If the PsbH protein and/or the D2 protein are likewise damaged and need to be replaced, the disassembly of the PSII core monomer is likely to be much more extensive.
Proteolytic degradation of damaged PSII subunits
There has been much experimental effort to identify the proteases involved in D1 protein degradation. Proteases of both the DegP family and the FtsH family have been assigned a role in D1 protein degradation and both these proteases have been localized to the stromal region of the thylakoid membrane (Andersson and Aro, 1997; Lindahl et al., 1996, 2000; Adam and Clarke, 2002; Kanervo et al., 2003; Silva et al., 2003). It has been assumed that the DegP2 protease is responsible for the primary cleavage of the D1 protein in the stromal loop connecting the transmembrane (TM) helices D and E and thus producing the 23 kDa N-terminal and the 10 kDa C-terminal fragments, whereas the FtsH protease would have a secondary role in degrading the primary cleavage fragments of the D1 protein (Haußühl et al., 2001). More recent studies, however, assign a role for FtsH as a protease capable of complete degradation of the damaged D1 protein (Bailey et al., 2002; Silva et al., 2003). It is reasonable to assume that the proteases of these two families are also involved in the degradation of the D2 and PsbH proteins upon their damage during PSII photoinhibition and repair.
Free PSII core proteins, with the exception of the CP43 protein, are very rarely present in the thylakoid membranes of mature leaves (Zhang et al., 2000; Suorsa et al., 2004) implying that the degradation of the damaged PSII subunits must be tightly co-ordinated with the synthesis of new subunits and their incorporation into the PSII complex. Only when the synthesis of new PSII subunits is blocked, for example, by a protein synthesis inhibitor, do the PSII centres in the stroma thylakoids collapse and those PSII proteins not being photodamaged become targeted for proteolytic degradation (Fig. 2).
De novo synthesis, co-translational assembly and C-terminal processing of the D1 protein
Constant damage and replacement of the D1 protein in PSII core monomers has made it possible to study the mechanisms of D1 protein replacement in isolated intact chloroplasts (van Wijk et al., 1997; Zhang et al., 1999, 2000) as well as in intact leaves (A Rokka et al., unpublished results). Combination of short 35S-Met pulse-labelling and chase experiments in intact isolated chloroplasts or in intact leaves with the subfractionation of PSII subassemblies by sucrose density centrifugation or 2D BN/SDS–PAGE, has revealed several individual assembly steps of PSII. The D1 protein was shown to be co-translationally inserted into the existing PSII complex composed at least of the D2 protein and the 
and ß subunits of Cyt b559 (Zhang et al., 1999). Evidence has been provided that the ribosome nascent D1 chain complex first interacts with the chloroplast signal recognition particle cpSRP54 (Nilsson et al., 1999), which targets the nascent D1 chain to the thylakoid membrane. After being targeted to the thylakoid membrane, the D1 protein elongation and membrane insertion occur concomitantly. The insertion of the elongating D1 protein into the thylakoid membrane is likely to involve a cpSecY translocon channel, as shown by cross-linking and immunoprecipitation experiments (Zhang et al., 2001). During the D1 elongation and translocation process, the TM segments of elongating nascent D1 protein exit laterally from the translocon and start interacting with other PSII core proteins. The slow rate of translation elongation and pausing of ribosomes (Kim et al., 1991) are likely to allow the escape of pairs of D1 TM helices from the cpSecY translocon channel, thereby making the interaction of D1 with D2 possible during translation elongation (Zhang et al., 2000; Zhang and Aro, 2002). After two TM segments of the D1 protein have been translated, the translocon channel apparently opens laterally and allows an interaction of the elongating D1 with the receptor complex composed of D2, Cyt b559, PsbI, and possibly also of CP47, whereas a strong interaction between D1 and D2 is achieved only after four TMs of the D1 protein have been translated (Zhang et al., 2000).
Although the initial assembly of D1 into PSII is a co-translational process, the formation of functional PSII complexes also depends on several post-translational assembly steps, including C-terminal processing of the precursor D1 protein and reassociation of the released protein subunits (see below). The D1 protein is synthesized as a precursor with a C-terminal extension of 9–16 amino acid residues (Diner et al., 1988). After termination of translation, the D1 protein is rapidly processed C-terminally by a lumenal protease CtpA (Bowyer et al., 1992; Anbudurai et al., 1994). Processing of the D1 protein precedes the assembly of the CP43 protein (Zhang et al., 2000) and only thereafter is the ligation of the oxygen evolving complex to the lumenal side of PSII possible (Bowyer et al., 1992).
The fate and reassembly of other PSII subunits during the photoinhibition repair cycle
Most of the PSII complexes under the repair process seem not to release the CP47 antenna pigment protein. However, the extent of PSII disassembly required for repair depends on the severity of the damage to the PSII core complex. If only the D1 protein must be replaced, the least amount of disassembly is required. However, recently, the small 9 kDa PsbH protein has also been suggested to have a role in the photoinhibition-repair cycle of PSII (Bergantino et al., 2003). It has also been noticed that this protein is frequently replaced with a de novo synthesized PsbH protein copy in the PSII core monomers during the light exposure of leaves (A Rokka et al., unpublished results). These experiments suggest a crucial role for the PsbH protein in the turnover of the D1 protein and are in line with observations made with cyanobacterial cells implying a role for PsbH, not only as a stabilizing subunit for formation of the QB pocket in the PSII complex but also in the initiation and completion of the PSII repair cycle (Bergantino et al., 2003).
If the D2 protein has likewise been degraded and requires a replacement in the PSII core complex, a much more extensive disassembly of the PSII complex can be expected. In such a case most of the LMW subunits of PSII are apparently also released from the core monomer. The first assembly step of PSII, identified in experiments following the biogenesis of PSII centres, is the D2/Cyt b559/PsbI complex. It is possible, however, that upon D2 degradation, the Cyt b559/PsbI/CP47 complex remains attached and the de novo synthesized D2 protein first associates with this subassembly of PSII. It has remained unclear whether the synthesis and assembly of the D2 protein occurs co-translationally as has been shown for the insertion of the elongating D1 protein into PSII (Zhang et al., 1999). However, neither the D2 nor the D1 protein has generally been found free in the thylakoid membrane supporting the co-translational and co-ordinated synthesis and assembly for both the D1 and D2 reaction centre proteins (Wollman et al., 1999; Zerges, 2000).
Recent assembly studies of the PSII centres, using both pulse-chase experiments (A Rokka et al., unpublished results) and various psb gene deletion mutants (Suorsa et al., 2004), have provided evidence that the LMW protein subunits, PsbH, PsbL, PsbM, PsbTc, PsbR, and probably also PsbJ, associate with the PSII subassembly composed of D1/D2/Cyt b559/PsbI/CP47. Apparently these six LMW proteins are essential for the stabilization of the D1/D2/Cyt b559/PsbI/CP47 subassembly of PSII and also for providing the structural integrity for the assembly of yet another set of proteins to the PSII complex. In the subsequent assembly step the CP43, PsbK, PsbZ, and PsbW proteins become distinguished in the PSII core monomer complex. Of the LMW proteins of PSII, the PsbL subunit is essential for the stable association of CP43 (Suorsa et al., 2004), the PsbJ subunit for water splitting and ligation of the oxygen-evolving proteins, but also for regulation of the acceptor side activity of the PSII complex (Hager et al., 2002, Regel et al., 2001; Swiatek et al., 2003; Suorsa et al., 2004). PsbK is apparently required for PSII core dimerization (Zheleva et al., 1998) and the PsbZ and PsbW proteins are essential for the association of the peripheral light-harvesting Chl a/b antenna proteins (Swiatek et al., 2001; A Rokka et al., unpublished results). It is not yet known whether all these protein subunits assemble into a PSII core monomer on the stroma thylakoid membranes. On the other hand, it is clear that stable PSII dimers with associated minor (CP29, CP26, CP24) and major (Lhcb1,2,3 proteins) LHCII antenna proteins are present only in the appressed grana membranes (Fig. 2).
|
Photoactivation of PSII and association of the oxygen-evolving complex (OEC) proteins |
|---|
|
TopAbstractLight-induced damage to PSII...Heterogeneity of the PSII...Photoactivation of PSII and...Role of PSII protein...References |
|---|
To regain the fully functional PSII complexes in the grana, a proper ligation of the Mn cluster and other inorganic cofactors, particularly the chloride and calcium ions, as well as the association of the OEC proteins are required. Ligation of the Mn cluster can already, in principle, take place on the stroma thylakoids since the PSII complexes including all proteins essential for ligation of the Mn cluster (Ferreira et al., 2004
), are present in stroma lamellae (Fig. 2). However, the quantum efficiency for photoactivation of PSII in limiting light was found to increase in direct proportion to the increase in the antenna size of the PSII complex (Ananyev et al., 2001). This suggests that association of the LHCII proteins, that is most likely limited to the grana appressions, also plays a role in the maintenance of the stable activation of PSII water splitting. This phenomenon is likely to be related to the in vivo stabilization of the Mn cluster by binding of the Ca2+ and Cl– ions and the protein components of OEC comprising the 33 kDa PsbO protein, the 23 kDa PsbP protein, and the 17 kDa PsbQ protein. When studying the association of the OEC proteins with the PSII complex, it was found that the smallest PSII subassembly harbouring the PsbO protein was the intact PSII core monomer (Suorsa et al., 2004). In this respect it is interesting that the CP43 protein was also found to be essential for association of PsbO, although in structural studies the lumenal loops of CP47 and the D2 proteins have been emphasized in docking of the PsbO protein (Nield et al., 2000). Because CP43 associates with the PSII subcomplex under repair in the stroma exposed membranes (Fig. 2) it is also possible that the association of PsbO and the photoactivation of PSII are occurring on stroma thylakoids, before the core monomers migrate back to the grana. On the other hand, there is experimental evidence indicating that the final stabilization of oxygen evolution by ligation of the two other OEC proteins, PsbP and PsbQ, to the PSII complex occurs mainly in the grana membrane, possibly after attachment of the LHCII complex and dimerization of the PSII core monomer (Hashimoto et al., 1997). |
Role of PSII protein phosphorylation in the photoinhibition-repair cycle |
|---|
|
TopAbstractLight-induced damage to PSII...Heterogeneity of the PSII...Photoactivation of PSII and...Role of PSII protein...References |
|---|
Exposure of leaves to light induces the phosphorylation of a number of PSII proteins in the thylakoid membrane (Bennett, 1991
), resulting from redox-dependent activation of several protein kinases. The N-terminal threonine (Thr) residues are phosphorylated in the D1 and D2 reaction centre proteins and the CP43 protein of the PSII core (Bennett, 1977, 1991), while two Thr-phosphorylation sites were recently reported for the PsbH protein (Vener et al., 2001). Furthermore, three out of the six pigment-binding proteins of the PSII light-harvesting Chl a/b antenna (Lhcb1, Lhcb2, and Lhcb4) become reversibly phosphorylated upon light–dark transitions (Bennett, 1991). The phosphorylation sites of the Lhcb1 and Lhcb2 proteins reside in the N-terminal Thr-residues (Michel et al., 1991; Vener et al., 2001). The Thr-residue number 83 was shown to become phosphorylated in mature maize Lhcb4 protein (Testi et al., 1996), whereas recently the Thr-residue number 6 was demonstrated as a phosphorylation site in Arabidopsis Lhcb4.2 protein (Hansson and Vener, 2003). Although the identification of the kinases involved is not yet clear, several redox-regulated serine/threonine protein kinases with at least partial substrate specificity for PSII core and antenna phosphoproteins, have been demonstrated in the thylakoid membrane, from which the thylakoid associated kinases (TAK) (Snyders and Kohorn, 2001) and the Stt7 kinase (Dèpege et al., 2003), being involved either directly or indirectly in the phosphorylation of the Lhcb1 and 2 proteins, are the best-characterized ones so far. Both soluble and membrane-bound phosphatases capable of dephosphorylating thylakoid phosphoproteins have also been found in chloroplasts (Sun et al., 1989; Hammer et al. 1997; Vener et al., 1999), but all these enzymes remain very poorly characterized.
Reduction of free plastoquinone in the thylakoid membrane initiates the activation of the kinases specific for phosphorylation of the PSII core and Lhcb phosphoproteins. Thus the various cellular processes that impact on the reduction state of the plastoquinone pool also exert control over the phosphorylation of both the PSII core and Lhcb phosphoproteins (Hou et al., 2002; Pursiheimo et al., 2001, 2003) and the steady-state phosphorylation level of proteins depends on counteracting activities of both the kinases and phosphatases.
Under unstressed conditions, the full phosphorylation of PSII core proteins is generally attained at irradiances corresponding to those experienced by the plant during growth or at irradiances exceeding those (Rintamäki et al., 1997). Thus, under the conditions of the highest rate of PSII photodamage and repair, the core proteins of PSII are generally phosphorylated, particularly those located in appressed thylakoid membranes (Baena-Gonzalez et al., 1999). A number of experimental data suggest that phosphorylation of the PSII core proteins regulates the PSII photoinhibition-repair cycle by controlling the timing of the proteolytic degradation of photodamaged D1 protein in the thylakoid membrane. It is assumed that under severe photoinhibition, when the ‘repair sites’ in stroma exposed membranes are fully occupied (Kettunen et al., 1997), the integrity of photodamaged PSII complexes in the grana regions is guaranteed by phosphorylation of the PSII core proteins, the D1, D2, and CP43 proteins. Preventing the collapse of photodamaged PSII complexes by phosphorylation in the grana region, prior to their migration to a repair site in non-appressed membranes, allows co-ordinated protein degradation, repair, and reassembly of the PSII complexes in the stroma-exposed membranes. Dephosphorylation of PSII subunits and partial disassembly of the PSII complex only occurs upon the damaged PSII complex entering the stroma thylakoids. Phospho-D1 and phospho-D2 proteins are not proteolytically degraded as efficiently as their non-phosphorylated counterparts (Koivuniemi et al., 1995; Rintamäki et al., 1996). Dephosphorylation indeed is a prerequisite for proteolytic degradation of damaged PSII subunits. Despite inducing phosphorylation, light also has an additional regulatory role, either for the migration of PSII complexes to stroma thylakoid regions or for dephosphorylation of the damaged PSII complex, as only in light do the damaged PSII complexes appear to undergo the repair process in the stroma exposed thylakoids (Rintamäki et al., 1996).
Finally, it is necessary to emphasize that phosphorylation of the Lhcb1 and Lhcb2 proteins, the major LHCII antenna proteins of PSII, occurs under low light and thus does not play any role in the PSII photoinhibition-repair cycle. In fact, the kinase involved in Lhcb1 and Lhcb2 protein phosphorylation becomes inhibited at moderate light intensities by thiol reductants that accumulate with increasing illumination, initially in the chloroplast stroma and subsequently attaching to the thylakoid membrane reducing the catalytically active disulphide bond in the kinase into catalytically inactive dithiol group (Rintamäki et al., 2000; Martinsuo et al., 2003). Although not connected to phosphorylation, it is evident that the LHCII antenna detaches from photodamaged PSII in grana appressions, prior to the monomerization of PSII core dimer and migration of the PSII core monomer to the stroma thylakoids for repair. The mechanism inducing this detachment of the LHCII antenna from the PSII core, however, remains unclear.
Although the phosphorylation of the major LHCII antenna proteins does not seem to play any role in PSII photodamage or repair, the phosphorylation of the minor LHCII antenna polypeptide Lhcb4 (CP29) has been assigned a role in the protection of the PSII centres against cold-induced photoinhibition in C4 plants (Bergantino et al., 1995). More recently, distinct phosphorylation sites in CP29 were found from C3 plants as well, suggesting a more widespread role of this phenomenon (Bergantino et al., 1998). It is intriguing that of all the LHCII proteins only the Lhcb4 protein phosphorylation requires strong reduction of the plastoquinone pool occurring at high light intensities (Pursiheimo et al., 2003) and is thus a relevant candidate to possess a functional role in the dissipation of excess excitation energy and in the protection of PSII against photodamage (Bassi et al., 1997; Mauro et al., 1997). The molecular mechanisms for such a dissipation of excitation energy by phospho-CP29 still remain to be investigated.
|
Acknowledgements |
|---|
Research in our laboratory has been supported by the Academy of Finland, The Finnish Ministry of Agriculture and Forestry, and the Nordiskt Kontaktorgan för Jurdbruksforskning.
|
References |
|---|
|
TopAbstractLight-induced damage to PSII...Heterogeneity of the PSII...Photoactivation of PSII and...Role of PSII protein...References |
|---|
Adam Z, Clarke AK. 2002. Cutting edge of chloroplast proteolysis. Trends in Plant Science 7, 451–456.[CrossRef][ISI][Medline]
Ananyev GM, Zaltsman L, Vasko C, Dismukes GC. 2001. The inorganic biochemistry of photosynthetic oxygen evolution/water oxidation. Biochimica et Biophysica Acta 1503, 52–68.[Medline]
Anbudurai PR, Mor TS, Ohad I, Shestakov SV, Pakrasi HB. 1994. The ctpA gene encodes the C-terminal processing protease for the D1 protein of the photosystem II reaction center complex. Proceedings of the National Academy of Sciences, USA 91, 8082–8086.
Anderson JM, Park YI, Chow WS. 1997. Photoinactivation and photoprotection of photosystem II in nature. Physiologia Plantarum 100, 314–323.
Andersson B, Aro E-M. 1997. Proteolytic activities and proteases of plant chloroplasts. Physiologia Plantarum 100, 780–793.
Aro EM, Virgin I, Andersson B. 1993. Photoinhibition of photosystem II: inactivation, protein damage and turnover. Biochimica et Biophysica Acta 1143, 113–134.[Medline]
Baena-Gonzalez E, Barbato R, Aro E-M. 1999. Role of PSII phosphorylation in the PSII repair cycle and oligomeric structure. Planta 208, 196–204.[CrossRef]
Bailey S, Thompson E, Nixon PJ, Horton P, Mullineaux CW, Robinson C, Mann NH. 2002. A critical role for the Var2 FtsH homologue of Arabidopsis thaliana in the photosystem II repair cycle in vivo. Journal of Biological Chemistry 277, 2006–2011.
Bassi R, Sandona D, Croce R. 1997. Novel aspects of chlorophyll a/b-binding proteins. Physiologia Plantarum 100, 769–779.
Bennett J. 1977. Phosphorylation of chloroplast membrane polypeptides. Nature 269, 344–346.
Bennett J. 1991. Protein phosphorylation in green plant chloroplasts. Annual Review of Plant Physiology and Plant Molecular Biology 42, 281–311.[CrossRef][ISI]
Bergantino E, Brunetta A, Touloupakis E, Segalla A, Szabò I, Giacometti GM. 2003. Role of the PSII-H subunit in photoprotection. Novel aspects of D1 turnover in Synechocystis 6803. Journal of Biological Chemistry 278, 41820–41829.
Bergantino E, Dainese P, Cerovic Z, Sechi S, Bassi R. 1995. A post-translational modification of the photosystem II subunit CP29 protects maize from cold stress. Journal of Biological Chemistry 270, 8474–8481.
Bergantino E, Sandona D, Cugini D, Bassi R. 1998. The photosystem II subunit CP29 can be phosphorylated in both C3 and C4 plants as suggested by sequence analysis. Plant Molecular Biology 36, 11–22.[CrossRef][ISI][Medline]
Bowyer JR, Packer JCL, McCormack BA, Whitelegge JP, Robinson C, Taylor M. 1992. Carboxyl-terminal processing of the D1 protein and photoactivation of water splitting in photosystem II. Journal of Biological Chemistry 267, 5424–5433.
Dèpege N, Bellafiore S, Rochaix JD. 2003. Role of chloroplast protein kinase Stt7 in LHCII phosphorylation and state transition in Chlamydomonas. Science 299, 1572–1575.
Diner BA, Ries DF, Cohen BN, Metz JG. 1988. COOH-terminal processing of polypeptide D1 of the photosystem II reaction center of Scenedesmus obliquus is necessary for the assembly of the oxygen-evolving complex. Journal of Biological Chemistry 263, 8972–8980.
Ferreira K, Iverson TM, Maghlaoui K, Barber J, Iwata S. 2004. Architecture of the photosynthetic oxygen-evolving center. Science 303, 1831–1838.
Guenther J, Melis A. 1990. The physiological significance of photosystem II heterogeneity in chloroplasts. Photosynthesis Research 23, 105–109.[CrossRef][ISI]
Hager M, Hermann M, Biehler K, Krieger-Liszkay A, Bock R. 2002. Lack of the small plastid-encoded PsbJ polypeptide results in a defective water-splitting apparatus of photosystem II, reduced photosystem I levels and hypersensitivity to light. Journal of Biological Chemistry 277, 14031–14039.
Hammer MF, Markwell J, Sarath G. 1997. Purification of a protein phosphatase from chloroplast stroma capable of dephosphorylating the light-harvesting complex- II. Plant Physiology 113, 227–233.[Abstract]
Hansson M, Vener AV. 2003. Identification of three previously unknown in vivo phosphorylation sites in thylakoid membranes of Arabidopsis thaliana. Molecular and Cellular Proteomics 2, 550–559.
Hashimoto A, Ettinger WF, Yamamoto Y, Theg SM. 1997. Assembly of newly incorporated oxygen-evolving complex subunits in isolated chloroplasts: sites of assembly and mechanism of binding. The Plant Cell 9, 441–452.[Medline]
Haußühl K, Andersson B, Adamska, I. 2001. A chloroplast DegP2 protease performs the primary cleavage of the photodamaged D1 protein in plant photosystem II. EMBO Journal 20, 1–10.[CrossRef][ISI][Medline]
Heinemeyer J, Eubel H, Wehmhöner D, Jänsch L, Braun H-P. 2004. Proteomic approach to characterize the supramolecular organization of photosystems in higher plants. Phytochemistry 65, 1683–1692.[CrossRef][ISI][Medline]
Herranen M, Battchikova N, Zhang P, Graf A, Sirpiö S, Paakkarinen V, Aro E-M. 2004. Towards functional proteomics of membrane protein complexes in Synechocystis sp. PCC 6803. Plant Physiology 134, 470–481.
Hou C-X, Pursiheimo S, Rintamäki E, Aro E-M. 2002. Environmental and metabolic control of LHCII protein phosphorylation: revealing the mechanisms for dual regulation of the LHCII kinase. Plant, Cell and Environment 25, 1515–1525.
Ivanov B, Khorobrykh S. 2003. Participation of photosynthetic electron transport in production and scavenging of reactive oxygen species. Antioxidant Redox Signaling 5, 43–53.
Jansen MAK, Greenberg BM, Edelman M, Mattoo AK, Gaba V. 1996. Accelerated degradation of the D2 protein of photosystem II under ultraviolet radiation. Photochemistry and Photobiology 63, 814–817.
Kanervo E, Spetea C, Nishiyama Y, Murata N, Andersson B, Aro E-M. 2003. Dissecting a cyanobacterial proteolytic system: efficiency in inducing degradation of the D1 protein of photosystem II in cyanobacteria and plants. Biochimica et Biophysica Acta 1607, 131–140.[Medline]
Koivuniemi A, Aro E-M, Andersson B. 1995. Degradation of the D1 and D2 proteins of photosystem II in higher plants is regulated by reversible phosphorylation. Biochemistry 34, 16022–16029.[CrossRef][Medline]
Kettunen R, Pursiheimo S, Rintamäki E, van Wijk KJ, Aro E-M. 1997. Transcriptional and translational adjustments of psbA gene expression in mature chloroplasts during photoinhibition and subsequent repair of photosystem II. European Journal of Biochemistry 247, 441–448.[ISI][Medline]
Kim J, Klein PG, Mullet JE. 1991. Ribosomes pause at specific sites during synthesis of membrane-bound chloroplast reaction centre protein D1. Journal of Biological Chemistry 266, 14931–14938.
Kyle DJ, Kuang TY, Watson JL, Arntzen CJ. 1984. Movement of a sub-population of the light-harvesting complez (LHCII) from grana to stroma lamellae as a consequence of its phosphorylation. Biochimica et Biophysica Acta 765, 89–96.
Laemmli UK. 1970. Cleavage of structural proteins during the assembly of head of bacteriophage T4. Nature 227, 680–685.[CrossRef][Medline]
Lindahl M, Tabak S, Cseke L, Pichersky E, Andersson B, Adam Z. 1996. Identification, characterization, and molecular cloning of a homologue of the bacterial FtsH protease in chloroplasts of higher plants. Journal of Biological Chemistry 271, 29329–29334.
Lindahl M, Spetea C, Hundal T, Oppenheim AB, Adam Z, Andersson B. 2000. The thylakoid FtsH protease plays a role in the light-induced turnover of the photosystem II D1 protein. The Plant Cell 12, 419–431.
Martinsuo P, Pursiheimo S, Aro E-M, Rintamäki E. 2003. Dithiol oxidant and disulfide reductant dynamically regulate the phosphorylation of light harvesting complex II proteins in thylakoid membranes. Plant Physiology 133, 37–46.
Mattoo AK, Hoffman-Falk H, Marder JB, Edelman M. 1984. Regulation of protein metabolism: coupling of photosynthetic electron transport to in vivo degradation of the rapidly metabolized 32-kilodalton protein of the chloroplast membranes. Proceedings of the National Academy of Sciences, USA 81, 1380–1384.
Mauro S, Dainese P, Lannoye R, Bassi R. 1997. Cold-resistant and cold-sensitive maize lines differ in the phosphorylation of the photosystem II subunit, CP29. Plant Physiology 115, 171–180.[Abstract]
Melis A. 1999. Photosystem-II damage and repair cycle in chloroplasts: what modulates the rate of photodamage in vivo? Trends in Plant Science 4, 130–135.[CrossRef][ISI][Medline]
Michel H, Griffin PR, Shabanowitz J, Hunt DF, Bennett J. 1991. Tandem mass spectrometry identifies sites of three post-translational modifications of spinach light-harvesting chlorophyll protein II. Proteolytic cleavage, acetylation, and phosphorylation. Journal of Biological Chemistry 266, 17584–17591.
Muller P, Li XP, Niyogi KK. 2001. Non-photochemical quenching. A response to excess light energy. Plant Physiology 125, 1558–1566.
Nield J, Kruse O, Ruprecht J, da Fonseca P, Büchel C, Barber J. 2000. Three-dimensional structure of Chlamydomonas reinhardtii and Synechococcus elongatus photosystem II complexes allows for comparison of their oxygen-evolving complex organization. Journal of Biological Chemistry 275, 27940–27946.
Nilsson R, Brunner J, Hoffman NE, van Wijk KJ. 1999. Interactions of ribosome nascent chain complexes of the chloroplast-encoded D1 thylakoid membrane protein with cpSRP54. EMBO Journal 18, 733–742.[CrossRef][ISI][Medline]
Prasil O, Adir N, Ohad I. 1992. Dynamics of photosystem II. Mechanism of photoinhibition and recovery processes. In: Barber K, ed. Topics in photosynthesis, Vol. II. The Netherlands: Elsevier, 293–348.
Pursiheimo S, Martinsuo P, Rintamäki E, Aro E-M. 2003. Photosystem II protein phosphorylation follows four distinctly different regulatory patterns induced by environmental cues. Plant, Cell and Environment 26, 1995–2003.
Pursiheimo S, Mulo P, Rintamäki E, Aro E-M. 2001. Coregulation of light-harvesting complex II phosphorylation and lhcb mRNA accumulation in winter rye. The Plant Journal 26, 317–327.[CrossRef][ISI][Medline]
Regel RE, Ivleva NB, Zer H, Meurer J, Shestakov SV, Herrmann RG, Pakrasi HB, Ohad I. 2001. Deregulation of electron flow within photosystem II in the absence of the PsbJ protein. Journal of Biological Chemistry 276, 41473–41478.
Rintamäki E, Kettunen R, Aro E-M. 1996. Differential D1 dephosphorylation in functional and photodamaged photosystem II centres. Dephosphorylation is a prerequisite for degradation of damaged D1*. Journal of Biological Chemistry 271, 14870–14875.
Rintamäki E, Salonen M, Suoranta U-M, Carlberg I, Andersson B, Aro E-M. 1997. Phosphorylation of light-harvesting complex II and photosystem II core proteins shows different irradiance-dependent regulation in vivo. Application of phosphothreonine antibodies to analysis of thylakoid phosphoproteins. Journal of Biological Chemistry 272, 30476–30482.
Rintamäki E, Martinsuo P, Pursiheimo S, Aro E-M. 2000. Cooperative regulation of light-harvesting complex II phosphorylation via the plastoquinol and the ferredoxin–thioredoxin system in chloroplasts. Proceedings of the National Academy of Sciences, USA 97, 11644–11649.
Sakurai I, Hagio M, Gombos Z, Tyystjärvi T, Paakkarinen V, Aro E-M, Wada H. 2003. Requirement of phosphatidylglycerol for maintenance of photosynthetic machinery. Plant Physiology 133, 1376–1384.
Silva P, Thompson E, Bailey S, Kruse O, Mullineaux CW, Robinson C, Mann NH, Nixon PJ. 2003. FtsH is involved in the early stages of repair of photosystem II in Synechocystis sp PCC 6803. The Plant Cell 15, 2152–2164.
Schuster G, Timberg R, Ohad I. 1988. Turnover of thylakoid photosystem II proteins during photoinhibition of Chlamydomonas reinhardtii. European Journal of Biochemistry 177, 403–410.[ISI][Medline]
Snyders S, Kohorn BD. 2001. Disruption of thylakoid-associated kinase 1 leads to alteration of light harvesting in Arabidopsis. Journal of Biological Chemistry 276, 32169–32176.
Sun G, Bailey D, Jones MW, Markwell J. 1989. Chloroplast thylakoid protein phosphatase is a membrane surface-associated activity. Plant Physiology 89, 238–243.
Suorsa M, Regel R, Paakkarinen V, Battchikova N, Herrmann RG, Aro E-M. 2004. Protein assembly of photosystem II and accumulation of subcomplexes in the absence of low molecular mass subunits PsbL and PsbJ. European Journal of Biochemistry 271, 96–107.[ISI][Medline]
Swiatek M, Kuras R, Sokolenko A, et al. 2001. The chloroplast gene ycf9 encodes a photosystem II (PSII) core subunit, PsbZ, that participates in PSII supramolecular architecture. The Plant Cell 13, 347–367.
Swiatek M, Regel R, Meurer J, Wanner G, Pakrasi HB, Ohad I, Herrmann RG. 2003. Effects of selective inactivation of individual genes for low-molecular-mass subunits on the assembly of photosystem II, as revealed by chloroplast transformation: the psbEFLJ operon in Nicotiana tabacum. Molecular and General Genomics 268, 699–710.
Testi MG, Croce R, Polverino-De Laureto P, Bassi R. 1996. A CK2 site is reversibly phosphorylated in the photosystem II subunit CP29. FEBS Letters 399, 245–250.[CrossRef][ISI][Medline]
Tyystjärvi E, Aro E-M. 1996. The rate constant of photoinhibition, measured in lincomycin-treated leaves, is directly proportional to light intensity. Proceedings of the National Academy of Sciences, USA 93, 2213–2218.
van Wijk KJ, Roobol-Boza M, Kettunen R, Andersson B, Aro E-M. 1997. Synthesis and assembly of the D1 protein into photosystem II: processing of C-terminus and identification of the initial assembly partners and complexes during photosystem II repair. Biochemistry 36, 6178–6186.[CrossRef][Medline]
Vener AV, Rokka A, Fulgosi H, Andersson B, Herrmann RG. 1999. A cyclophilin-regulated PP2A-like protein phosphatase in thylakoid membranes of plant chloroplasts. Biochemistry 38, 14955–14965.[CrossRef][Medline]
Vener AV, Harms A, Sussman R, Vierstra RD. 2001. Mass spectrometric resolution of reversible protein phosphorylation in photosynthetic membranes of Arabidopsis thaliana. Journal of Biological Chemistry 276, 6959–6966.
Wollman F-A, Minai L, Nechushtai R. 1999. The biogenesis and assembly of photosynthetic proteins in thylakoid membranes. Biochimica et Biophysica Acta 1411, 21–85.[Medline]
Zerges W. 2000. Translation in chloroplasts. Biochimie 82, 583–601.[Medline]
Zhang L, Aro E-M. 2002. Synthesis, membrane insertion and assembly of the chloroplast-encoded D1 protein into photosystem II. FEBS Letters 512, 13–18.[CrossRef][ISI][Medline]
Zhang L, Paakkarinen V, Suorsa M, Aro E-M. 2001. A SecY homologue is involved in chloroplast-encoded D1 protein biogenesis. Journal of Biological Chemistry 276, 37809–37814.
Zhang L, Paakkarinen V, van Wijk KJ, Aro E-M. 1999. Co-translational assembly of the D1 protein into photosystem II. Journal of Biological Chemistry 274, 16062–16067.
Zhang L, Paakkarinen V, van Wijk KJ, Aro E-M. 2000. Biogenesis of the chloroplast-encoded D1 protein: regulation of translation elongation, insertion, and assembly into photosystem II. The Plant Cell 12, 1769–1781.
Zheleva D, Sharma J, Panico M, Morris HR, Barber J. 1998. Isolation and characterization of monomeric and dimeric CP47-reaction center photosystem II complexes. Journal of Biological Chemistry 273, 16122–16127.
Zouni A, Witt HT, Kern J, Fromme P, Krauss N, Saenger W, Orth P. 2001. Crystal structure of photosystem II from Synechococcus elongatus at 3.8 Å resolution. Nature 409, 739–743.[CrossRef][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  E. Romanowska, J. Kargul, M. Powikrowska, G. Finazzi, J. Nield, A. Drozak, and B. Pokorska Structural Organization of Photosynthetic Apparatus in Agranal Chloroplasts of Maize J. Biol. Chem., September 19, 2008; 283(38): 26037 - 26046. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Majeran, B. Zybailov, A. J. Ytterberg, J. Dunsmore, Q. Sun, and K. J. van Wijk Consequences of C4 Differentiation for Chloroplast Membrane Proteomes in Maize Mesophyll and Bundle Sheath Cells Mol. Cell. Proteomics, September 1, 2008; 7(9): 1609 - 1638. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Rutschow, A. J. Ytterberg, G. Friso, R. Nilsson, and K. J. van Wijk Quantitative Proteomics of a Chloroplast SRP54 Sorting Mutant and Its Genetic Interactions with CLPC1 in Arabidopsis Plant Physiology, September 1, 2008; 148(1): 156 - 175. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Komenda, J. Nickelsen, M. Tichy, O. Prasil, L. A. Eichacker, and P. J. Nixon The Cyanobacterial Homologue of HCF136/YCF48 Is a Component of an Early Photosystem II Assembly Complex and Is Important for Both the Efficient Assembly and Repair of Photosystem II in Synechocystis sp. PCC 6803 J. Biol. Chem., August 15, 2008; 283(33): 22390 - 22399. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Shimizu, L. Peng, F. Myouga, R. Motohashi, K. Shinozaki, and T. Shikanai CRR23/NdhL is a Subunit of the Chloroplast NAD(P)H Dehyd |