9w5b | pdb_00009w5b
cryo-EM structure of PSII D1-S264V from Thermosynechococcus vestitus BP-1
Structural highlights
FunctionPSBA3_THEVB Photosystem II (PSII) is a light-driven water:plastoquinone oxidoreductase that uses light energy to abstract electrons from H(2)O, generating O(2) and a proton gradient subsequently used for ATP formation. It consists of a core antenna complex that captures photons, and an electron transfer chain that converts photonic excitation into a charge separation. The D1/D2 (PsbA/PsbD) reaction center heterodimer binds P680, the primary electron donor of PSII as well as several subsequent electron acceptors.[HAMAP-Rule:MF_01379][1] Publication Abstract from PubMedPhotosystem II (PSII) catalyzes water oxidation and oxygen evolution by a light-induced electron transfer chain, leading to the generation of electrons, protons and dioxygen. D1-S264 is a residue located close to the Q(B)-binding site, and mutation of this residue has been shown to bring significant effects on the electron transfer and oxygen-evolving activities. Here we analyzed the structure of a Thermosynechococcus elongatus mutant PsbA3-S264V by cryo-electron microscopy at 1.96 A resolution, which showed significant changes in the structure surrounding the bicarbonate and Q(B)-binding region. Due to change of Ser to Val, the hydrogen-bond between the Q(B) carbonyl oxygen and S264 is altered, which changed the protonation pathway of Q(B) from the original route of D1-H252 through D1-S264 to Q(B), to a new, longer and less efficient route of D1-H252 through D1-F265 to Q(B). Two residues, D1-E244 and D2-E242, changed their side chain orientations significantly. Among them, D2-E242 adopted two conformations, and both are largely deviated from the original structure. All these changes led to alterations in hydrogen-bonding networks of two channels, channel A and channel B, that connect the stromal surface to Q(B) and may function to transport protons to protonate Q(B). Furthermore, isothermal titration calorimetry experiments showed a diminished 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) binding affinity of the mutated PSII, which may be explained by a structural rotation of D1-F255 in the mutant based on structural analysis of DCMU-bound PSII. These findings offer valuable insights into the functions of D1-S264 in Q(B) protonation and function, as well as in the DCMU-binding. Structural and functional analysis of a photosystem II mutant PsbA3-S264V.,Fan S, Nakajima Y, Kato K, Jiang H, Tsai PC, Jia A, Sugiura M, Shen JR Biochim Biophys Acta Bioenerg. 2026 Sep 6;1868(1):149607. doi: , 10.1016/j.bbabio.2026.149607. PMID:42702229[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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