TAILIEUCHUNG - Báo cáo khoa học: Stoichiometry of LHCI antenna polypeptides and characterization of gap and linker pigments in higher plants Photosystem I

We report on the results obtained by measuring the stoi-chiometry of antenna polypeptides in Photosystem I (PSI) fromArabidopsis thaliana. This analysis was performed by quantification of Coomassie blue binding to individual LHCI polypeptides, fractionation by SDS/PAGE, and by the use of recombinant light harvesting complex of Photo-system I (Lhca) holoproteins as a standard reference. Our results show that a single copy of each Lhca1–4 polypeptide is present in Photosystem I. | Eur. J. Biochem. 271 4659-4665 2004 FEBS 2004 doi Stoichiometry of LHCI antenna polypeptides and characterization of gap and linker pigments in higher plants Photosystem I Matteo Ballottari1 Chiara Govoni1 Stefano Caffarri2 1 and Tomas Morosinotto1 2 1 Dipartimento Scientifico e Tecnologico Universita di Verona Verona Italy 2Université Aix-Marseille II LGBP- Faculte des Sciences de Luminy Departement de Biologie Marseille France We report on the results obtained by measuring the stoichiometry of antenna polypeptides in Photosystem I PSI from Arabidopsis thaliana. This analysis was performed by quantification of Coomassie blue binding to individual LHCI polypeptides fractionation by SDS PAGE and by the use of recombinant light harvesting complex of Photosystem I Lhca holoproteins as a standard reference. Our results show that a single copy of each Lhca1-4 polypeptide is present in Photosystem I. This is in agreement with the recent structural data on PSI-LHCI complex Ben Shem A. Frolow F. and Nelson N. 2003 Nature 426 630-635 . The discrepancy from earlier estimations based on pigment binding and yielding two copies of each LHCI polypeptide per PSI is explained by the presence of gap and linker chlorophylls bound at the interface between PSI core and LHCI. We showed that these chlorophylls are lost when LHCI is detached from the PSI core moiety by detergent treatment and that gap and linker chlorophylls are both Chl a and Chl b. Carotenoid molecules are also found at this interface between LHCI and PSI core. Similar experiments performed on PSII supercomplexes showed that dissociation into individual pigment-proteins did not produce a significant loss of pigments suggesting that gap and linker chlorophylls are a peculiar feature of Photosystem I. Keywords chlorophyll Coomassie staining LHCI photosystem stoichiometry. Photosystem I PSI is a multisubunit complex located in thylakoid membranes acting as a light-dependent .

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