JXB Advance Access originally published online on July 15, 2008
Journal of Experimental Botany 2008 59(12):3259-3269; doi:10.1093/jxb/ern177
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© 2008 The Author(s).
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RESEARCH PAPER |
Hexameric oligomerization of mitochondrial peroxiredoxin PrxIIF and formation of an ultrahigh affinity complex with its electron donor thioredoxin Trx-o
1Biochemistry and Physiology of Plants, W5-134, Bielefeld University, D-33501 Bielefeld, Germany
2Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, E-18008, Granada, Spain
3Department of Biochemistry and Cellular and Molecular Biology of Plants, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, E-18008, Granada, Spain
4Stress Biology and Plant Pathology, Centro de Edafologia y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, E-30100, Murcia, Spain
* To whom correspondence should be addressed. E-mail: sergio.barranco{at}uni-bielefeld.de
Mitochondria from plants, yeast, and animals each contain at least one peroxiredoxin (Prx) that is involved in peroxide detoxification and redox signalling. The supramolecular dynamics of atypical type II Prx targeted to the mitochondrion was addressed in pea. Microcalorimetric (ITC) titrations identified an extremely high-affinity binding between the mitochondrial PsPrxIIF and Trx-o with a KD of 126±14 pM. Binding was driven by a favourable enthalpy change (
H= –60.6 kcal mol–1) which was counterbalanced by unfavourable entropy changes (TS= –47.1 kcal mol–1). This is consistent with the occurrence of large conformational changes during binding which was abolished upon site-directed mutaganesis of the catalytic C59S and C84S. The redox-dependent interaction was confirmed by gel filtration of mitochondrial extracts and co-immunoprecipitation from extracts. The heterocomplex of PsPrxIIF and Trx-o reduced peroxide substrates more efficiently than free PsPrxIIF suggesting that Trx-o serves as an efficient and specific electron donor to PsPrxIIF in vivo. Other Trx-s tested by ITC analysis failed to interact with PsPrxIIF indicating a specific recognition of PsPrxIIF by Trx-o. PsPrxIIF exists primarily as a dimer or a hexamer depending on the redox state. In addition to the well-characterized oligomerization of classical 2-Cys Prx the results also show that atypical Prx undergo large structural reorganization with implications for protein–protein interaction and function.
Key words: Binding, mitochondria, peroxiredoxin, plant, redox, thioredoxin
Received 12 March 2008; Revised 21 May 2008 Accepted 5 June 2008
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