Distinct structural modulation of photosystem I and lipid environment stabilizes its tetrameric assembly.

Ming Chen, Annemarie Perez-Boerema, Laixing Zhang, Yanxue Li, Maojun Yang, Shizhong Li, Alexey Amunts

Nature plants 2020 Mar

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Photosystem I (PSI) is able to form different oligomeric states across various species. To reveal the structural basis for PSI dimerization and tetramerization, we structurally investigated PSI from the cyanobacterium Anabaena. This revealed a disrupted trimerization domain due to lack of the terminal residues of PsaL in the lumen, which resulted in PSI dimers with loose connections between monomers and weaker energy-coupled chlorophylls than in the trimer. At the dimer surface, specific phospholipids, cofactors and interactions in combination facilitated recruitment of another dimer to form a tetramer. Taken together, the relaxed luminal connections and lipid specificity at the dimer interface account for membrane curvature. PSI tetramer assembly appears to increase the surface area of the thylakoid membrane, which would contribute to PSI crowding.

Citation

Ming Chen, Annemarie Perez-Boerema, Laixing Zhang, Yanxue Li, Maojun Yang, Shizhong Li, Alexey Amunts. Distinct structural modulation of photosystem I and lipid environment stabilizes its tetrameric assembly. Nature plants. 2020 Mar;6(3):314-320