Excited-State Dynamics in Photosystem II: Insights from the X-ray Crystal Structure

The heart of oxygenic photosynthesis is photosystem II (PSII), a multisubunit protein complex that uses solar energy to drive the splitting of water and production of molecular oxygen. The effectiveness of the photochemical reaction center of PSII depends on the efficient transfer of excitation ener...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2001-07, Vol.98 (15), p.8602-8607
Main Authors: Vasil'ev, S, Orth, P, Zouni, A, Owens, T G, Bruce, D
Format: Article
Language:English
Subjects:
Antennas
Biochemistry
Biological Sciences
Charge separation
Chlorophylls
Chromophores
Crystallography, X-Ray
Crystals
Cyanobacteria - chemistry
Electron transfer
Electron Transport
Energy Transfer
Kinetics
Modeling
Photosynthesis
Photosynthetic Reaction Center Complex Proteins - chemistry
Photosynthetic Reaction Center Complex Proteins - metabolism
Physics
Pigments
Protein Conformation
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Summary:The heart of oxygenic photosynthesis is photosystem II (PSII), a multisubunit protein complex that uses solar energy to drive the splitting of water and production of molecular oxygen. The effectiveness of the photochemical reaction center of PSII depends on the efficient transfer of excitation energy from the surrounding antenna chlorophylls. A kinetic model for PSII, based on the x-ray crystal structure coordinates of 37 antenna and reaction center pigment molecules, allows us to map the major energy transfer routes from the antenna chlorophylls to the reaction center chromophores. The model shows that energy transfer to the reaction center is slow compared with the rate of primary electron transport and depends on a few bridging chlorophyll molecules. This unexpected energetic isolation of the reaction center in PSII is similar to that found in the bacterial photosystem, conflicts with the established view of the photophysics of PSII, and may be a functional requirement for primary photochemistry in photosynthesis. In addition, the model predicts a value for the intrinsic photochemical rate constant that is 4 times that found in bacterial reaction centers.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.141239598