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Title | Structure of a photosystem I-ferredoxin complex from a marine cyanobacterium provides insights into far-red light photoacclimation. |
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Journal, issue, pages | J Biol Chem, Vol. 298, Issue 1, Page 101408, Year 2022 |
Publish date | Nov 15, 2021 |
Authors | Christopher J Gisriel / David A Flesher / Gaozhong Shen / Jimin Wang / Ming-Yang Ho / Gary W Brudvig / Donald A Bryant / |
PubMed Abstract | Far-red light photoacclimation exhibited by some cyanobacteria allows these organisms to use the far-red region of the solar spectrum (700-800 nm) for photosynthesis. Part of this process includes ...Far-red light photoacclimation exhibited by some cyanobacteria allows these organisms to use the far-red region of the solar spectrum (700-800 nm) for photosynthesis. Part of this process includes the replacement of six photosystem I (PSI) subunits with isoforms that confer the binding of chlorophyll (Chl) f molecules that absorb far-red light (FRL). However, the exact sites at which Chl f molecules are bound are still challenging to determine. To aid in the identification of Chl f-binding sites, we solved the cryo-EM structure of PSI from far-red light-acclimated cells of the cyanobacterium Synechococcus sp. PCC 7335. We identified six sites that bind Chl f with high specificity and three additional sites that are likely to bind Chl f at lower specificity. All of these binding sites are in the core-antenna regions of PSI, and Chl f was not observed among the electron transfer cofactors. This structural analysis also reveals both conserved and nonconserved Chl f-binding sites, the latter of which exemplify the diversity in FRL-PSI among species. We found that the FRL-PSI structure also contains a bound soluble ferredoxin, PetF1, at low occupancy, which suggests that ferredoxin binds less transiently than expected according to the canonical view of ferredoxin-binding to facilitate electron transfer. We suggest that this may result from structural changes in FRL-PSI that occur specifically during FRL photoacclimation. |
External links | J Biol Chem / PubMed:34793839 / PubMed Central |
Methods | EM (single particle) |
Resolution | 2.91 Å |
Structure data | EMDB-24821, PDB-7s3d: |
Chemicals | ChemComp-CL0: ChemComp-CLA:
ChemComp-F6C: ChemComp-PQN: ChemComp-SF4: ChemComp-BCR: ChemComp-LHG: ChemComp-LMG: ChemComp-LMT: ChemComp-CL: ChemComp-CA: ChemComp-FES: ChemComp-HOH: |
Source |
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Keywords | PHOTOSYNTHESIS / Photosystem I / Far-red light photoacclimation / Chlorophyll f / Ferredoxin / PsaF / PsaJ |