Chapter 16 - Photosystem II, a Structural Perspective

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Chapter 16 - Photosystem II, a Structural Perspective. In Harris, E. H., D., P., Stern, D. B., D., P., George B. Witman, . & D., P. (editors), The Chlamydomonas Sourcebook (Second Edition). London : Academic Press.
The Chlamydomonas Sourcebook (Second Edition) Publishers Summary: This chapter elucidates the structure and function of the photosystem II (PS II) apparatus. PS II, a multi-subunit protein–cofactor complex is overviewed with D1, D2 polypeptides, P680 the primary donor and pheophytins. QA and QB, the stable electron acceptor of photosystem II and the herbicide-binding site is elaborated with the view of non-heme iron. Models for the PS II complex are discussed in the context of the partial reactions leading to the trapping of excited states, charge separation, and the generation of molecular oxygen and reduced plastoquinone. PS II is a multi-subunit protein–cofactor complex embedded in the thylakoid membranes, which catalyzes the oxidation of water and the reduction of plastoquinone. The holocomplex consists of no less than 20 protein subunits and has at least 77 cofactors. X-ray diffraction studies have led to the elucidation of cofactor–protein interactions at near-atomic resolution. The electron-deficient primary donor P680 + is subsequently reduced via a four-step (S-state transitions) oxidation of water to molecular oxygen by the water-oxidizing complex (also known as the oxygen-evolving complex, OEC) that includes an Mn4-Ca cluster, finally P680+ is reduced and becomes available for another round of the light-driven charge separation.

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