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-Structure paper
| タイトル | Structure of a mutated photosystem II complex reveals changes to the hydrogen-bonding network that affect proton egress during O-O bond formation. |
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| ジャーナル・号・ページ | J Biol Chem, Vol. 301, Issue 3, Page 108272, Year 2025 |
| 掲載日 | 2025年2月6日 |
著者 | David A Flesher / Jieun Shin / Richard J Debus / Gary W Brudvig / ![]() |
| PubMed 要旨 | Photosystem II (PSII) is the water-splitting enzyme of oxygenic photosynthesis. Using light energy, PSII catalytically oxidizes two water molecules to fuel downstream metabolism, forming an O-O bond ...Photosystem II (PSII) is the water-splitting enzyme of oxygenic photosynthesis. Using light energy, PSII catalytically oxidizes two water molecules to fuel downstream metabolism, forming an O-O bond and releasing O as a byproduct. The reaction mechanism requires the strategic removal of four protons via conserved hydrogen-bonding networks, but these pathways remain poorly understood. Site-directed mutagenesis has been used to study these pathways and the role of specific side chains, such as Lys317 of the D2 subunit. Previous studies showed that the D2-Lys317Ala substitution, which abolishes the flexible hydrogen-bonding -NH group, resulted in delayed O release kinetics and diminished catalytic turnover, suggesting Lys317 has a crucial role in facilitating proton egress. Here, we investigated this proton egress pathway by determining the cryo-EM structure of PSII containing the D2-Lys317Ala substitution at a resolution of 1.97 Å. We observed that four new water molecules fill the space previously occupied by Lys317, but these waters lack specific water-protein interactions, leading to heterogeneity and suboptimal hydrogen bonding. We hypothesize that these waters negatively contribute to the existing hydrogen-bonding network and increase the entropic barrier for proton transfer. Additionally, we observed that a conserved chloride ion (Cl1), which is associated with Lys317, is unexpectedly maintained in D2-Lys317Ala PSII. However, unlike in wild-type, Cl1 has no measured effect on oxygen-evolution rates in D2-Lys317Ala PSII. This suggests that the role of Cl1 is dependent on the Lys317 amino group. These findings provide new insight into proton egress through the Cl1 hydrogen-bonding channel. |
リンク | J Biol Chem / PubMed:39922494 / PubMed Central |
| 手法 | EM (単粒子) |
| 解像度 | 1.97 Å |
| 構造データ | EMDB-48046, PDB-9eh5: |
| 化合物 | ![]() ChemComp-OEX: ![]() ChemComp-FE2: ![]() ChemComp-CL: ![]() ChemComp-CLA: ![]() ChemComp-BCR: ![]() ChemComp-LMG: ![]() ChemComp-PL9: ![]() ChemComp-SQD: ![]() ChemComp-LMT: ![]() ChemComp-BCT: ![]() ChemComp-LHG: ![]() ChemComp-DGD: ![]() ChemComp-HEM: ![]() ChemComp-RRX: ![]() ChemComp-CA: ![]() ChemComp-HOH: |
| 由来 |
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キーワード | PHOTOSYNTHESIS / photosystem II / oxygen-evolving complex / transition metals / metalloenzyme / mutagenesis / water channel / hydrogen-bond network |
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