Association of Photosystem I and Light-Harvesting Complex II during State Transitions
Green plant photosystem I (PS I) not only binds a chlorophyll a/b-binding, membrane-intrinsic antenna complex (LHCI) that is associated with the PS I core complex under almost all physiological conditions, but it can also transiently bind the major chlorophyll a/b-binding light-harvesting complex (LHCII), when the light conditions favor excitation of photosystem II (PS II) and the photosynthetic apparatus is in the so-called state 2. Recently, a low-resolution structure was obtained of a PS I–LHCII supercomplex from Arabidopsis thaliana. We describe here some of the structural features of this transient complex, and discuss the role of small PS I subunits that are involved in the binding of LHCII.We also discuss structural features of the PS I complex of the green algae Chlamydomonas reinhardtii, which has a larger LHCI antenna and shows a more pronounced difference between state 1 and state 2.
KeywordsThylakoid Membrane Protein Trimeric LHCII LHCII Complex Cyclic Electron Transfer Monomeric LHCII
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