Orientational Jahn-Teller Isomerism in the Dark-Stable State of Nature's Water Oxidase.

ABSTRACT: The tetramanganese-calcium cluster of the oxygen-evolving complex of photosystem II adopts electronically and magnetically distinct but interconvertible valence isomeric forms in its first light-driven oxidized catalytic state, S₂ . This bistability is implicated in gating the final catalytic states preceding O-O bond formation, but it is unknown how the biological system enables its emergence and controls its effect. Here we show that the Mn₄ CaO₅ cluster in the resting (dark-stable) S₁ state adopts orientational Jahn-Teller isomeric forms arising from a directional change in electronic configuration of the "dangler" Mn^III ion. The isomers are consistent with available structural data and explain previously unresolved electron paramagnetic resonance spectroscopic observations on the S₁ state. This unique isomerism in the resting state is shown to be the electronic origin of valence isomerism in the S₂ state, establishing a functional role of orientational Jahn-Teller isomerism unprecedented in biological or artificial catalysis.

SUBMITTER: Drosou M 

PROVIDER: S-EPMC8252073 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature