PARENT SESSION
Posters P2A Type I reaction centres. Abstracts (181-218)

Probing the active electron transfer branch in Photosystem I reaction center from Synechocystis sp. PCC 6803 by means of ultrafast spectroscopy. Naranbaatar Dashdorj^*,1, Wu Xu², John Golbeck³, Parag Chitnis², Sergei Savikhin¹, ¹ Department of Physics, West Lafayette, IN, USA² Department of Biochemistry, Biophysics, and Molecular Biology, Ames, IA, USA³ Department of Biochemistry and Molecular Biology, University Park, PA, USA

ABSTRACT- According to the X-ray crystal structure of the PS I complex, the reaction center cofactors are coordinated by heterodimeric transmembrane polypeptides PsaA and PsaB in pseudo-C₂ symmetrical branches. Whether the light-induced electron transfer occurs along one or both of the branches is still under debate. We addressed this problem by introducing branch-specific point-mutations near the primary acceptor A₀ and monitoring picosecond electron transfer dynamics from A₀ to the secondary electron acceptor A₁. The results demonstrate that mutations in the A branch significantly alter the kinetics of electron transfer while the complimentary mutations in the B branch have no effect on energy and electron transfer dynamics in PS I. We conclude that the light-induced electron transfer in PS I from Synechocystis sp. PCC 6803 occurs exclusively along the A branch.

KEY WORDS: Branch Problem, Photosynthesis, Photosystem I, Synechocystis sp.