JXB Advance Access originally published online on March 28, 2008
Journal of Experimental Botany 2008 59(6):1327-1340; doi:10.1093/jxb/ern039
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Peripheral membrane proteins mediate binding of vacuolar storage proteins to membranes of the secretory pathway of developing pea cotyledons
1Strukturelle Zellphysiologie, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Georg-August Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
2Biochemie der Pflanze, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Georg-August-Universität Göttingen, Justus-von-Liebig Weg 11, 37077 Göttingen, Germany
3Zellbiologie, Heidelberger Institut für Pflanzenwissenschaften, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
* To whom correspondence should be addressed. E-mail: giselbert.hinz{at}uni-heidelberg.de
In developing pea cotyledons, storage proteins are sorted via dense vesicles into the protein storage vacuole. Formation of these unique transport vesicles is characterized by aggregation of their cargo proteins. Protein sorting into dense vesicles is pH dependent. In order to gain insight into the molecular basis of storage protein sorting, a membrane binding assay was developed which allows for a detailed biochemical analysis of binding events. Employing this assay it was possible to show that storage proteins bind in a pH-dependent manner to the membranes of the secretory pathway with a pH optimum in the range of the lumenal pH of the Golgi cisternae. Through reconstitution experiments, it was possible to demonstrate further that this recruitment occurs via the interaction of peripheral rather than intrinsic membrane proteins. Results of co-immunoprecipitation experiments point to interactions between different storage proteins in the secretory system. These results are discussed in terms of the aggregation-mediated sorting of storage proteins into maturing dense vesicles.
Key words: Dense vesicles, Golgi apparatus, legumin, pea, receptor, sorting
Received 22 January 2008; Revised 22 January 2008 Accepted 23 January 2008