7dz7
State transition supercomplex PSI-LHCI-LHCII from double phosphatase mutant pph1;pbcp of green alga Chlamydomonas reinhardtii
Structural highlights
FunctionPSAA_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 PubMedIn green algae and plants, state transitions serve as a short-term light-acclimation process in the regulation of the light-harvesting capacity of photosystems I and II (PSI and PSII, respectively). During the process, a portion of light-harvesting complex II (LHCII) is phosphorylated, dissociated from PSII and binds with PSI to form the supercomplex PSI-LHCI-LHCII. Here, we report high-resolution structures of PSI-LHCI-LHCII from Chlamydomonas reinhardtii, revealing the mechanism of assembly between the PSI-LHCI complex and two phosphorylated LHCII trimers containing all four types of LhcbM protein. Two specific LhcbM isoforms, namely LhcbM1 and LhcbM5, directly interact with the PSI core through their phosphorylated amino terminal regions. Furthermore, biochemical and functional studies on mutant strains lacking either LhcbM1 or LhcbM5 indicate that only LhcbM5 is indispensable in supercomplex formation. The results unravel the specific interactions and potential excitation energy transfer routes between green algal PSI and two phosphorylated LHCIIs. Structural basis of LhcbM5-mediated state transitions in green algae.,Pan X, Tokutsu R, Li A, Takizawa K, Song C, Murata K, Yamasaki T, Liu Z, Minagawa J, Li M Nat Plants. 2021 Aug;7(8):1119-1131. doi: 10.1038/s41477-021-00960-8. Epub 2021 , Jul 8. PMID:34239095[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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