6ijj
From Proteopedia
Photosystem I of Chlamydomonas reinhardtii
Structural highlights
FunctionPSAB_CHLRE PsaA and PsaB bind P700, the primary electron donor of photosystem I (PSI), as well as the electron acceptors A0, A1 and FX. PSI is a plastocyanin/cytochrome c6-ferredoxin oxidoreductase, converting photonic excitation into a charge separation, which transfers an electron from the donor P700 chlorophyll pair to the spectroscopically characterized acceptors A0, A1, FX, FA and FB in turn. Oxidized P700 is reduced on the lumenal side of the thylakoid membrane by plastocyanin or cytochrome c6. Both potential cofactor branches in PSI seem to be active; however, electron transfer seems to proceed preferentially down the path including the phylloquinone bound by PsaA. Publication Abstract from PubMedDuring oxygenic photosynthesis, photosystems I and II (PSI and PSII) are essential for light-driven electron transport. Excitation energy transfer in PSI occurs extremely quickly, making it an efficient energy converter. In the alga Chlamydomonas reinhardtii (Cr), multiple units of light-harvesting complex I (LHCI) bind to the PSI core and function as peripheral antennae, forming a PSI-LHCI supercomplex. CrPSI-LHCI shows significantly larger antennae compared with plant PSI-LHCI while maintaining highly efficient energy transfer from LHCI to PSI. Here, we report structures of CrPSI-LHCI, solved by cryo-electron microscopy, revealing that up to ten LHCIs are associated with the PSI core. The structures provide detailed information about antenna organization and pigment arrangement within the supercomplexes. Highly populated and closely associated chlorophylls in the antennae explain the high efficiency of light harvesting and excitation energy transfer in CrPSI-LHCI. Antenna arrangement and energy transfer pathways of a green algal photosystem-I-LHCI supercomplex.,Su X, Ma J, Pan X, Zhao X, Chang W, Liu Z, Zhang X, Li M Nat Plants. 2019 Mar;5(3):273-281. doi: 10.1038/s41477-019-0380-5. Epub 2019 Mar , 8. PMID:30850819[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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Categories: Chlamydomonas reinhardtii | Large Structures | Li M | Liu Z | Ma J | Pan X | Su X | Zhang X
