Structural highlights
Function
PSAA_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 PubMed
In plants and green algae, the core of photosystem I (PSI) is surrounded by a peripheral antenna system consisting of light-harvesting complex I (LHCI). Here we report the cryo-electron microscopic structure of the PSI-LHCI supercomplex from the green alga Chlamydomonas reinhardtii. The structure reveals that eight Lhca proteins form two tetrameric LHCI belts attached to the PsaF side while the other two Lhca proteins form an additional Lhca2/Lhca9 heterodimer attached to the opposite side. The spatial arrangement of light-harvesting pigments reveals that Chlorophylls b are more abundant in the outer LHCI belt than in the inner LHCI belt and are absent from the core, thereby providing the downhill energy transfer pathways to the PSI core. PSI-LHCI is complexed with a plastocyanin on the patch of lysine residues of PsaF at the luminal side. The assembly provides a structural basis for understanding the mechanism of light-harvesting, excitation energy transfer of the PSI-LHCI supercomplex and electron transfer with plastocyanin.
Structure of the green algal photosystem I supercomplex with a decameric light-harvesting complex I.,Suga M, Ozawa SI, Yoshida-Motomura K, Akita F, Miyazaki N, Takahashi Y Nat Plants. 2019 Jun;5(6):626-636. doi: 10.1038/s41477-019-0438-4. Epub 2019 Jun , 10. PMID:31182847[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Suga M, Ozawa SI, Yoshida-Motomura K, Akita F, Miyazaki N, Takahashi Y. Structure of the green algal photosystem I supercomplex with a decameric light-harvesting complex I. Nat Plants. 2019 Jun;5(6):626-636. doi: 10.1038/s41477-019-0438-4. Epub 2019 Jun , 10. PMID:31182847 doi:http://dx.doi.org/10.1038/s41477-019-0438-4
