An oxyl/oxo mechanism for oxygen-oxygen coupling in PSII revealed by an x-ray free-electron laser.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31624207.
- Also identified by DOI 10.1126/science.aax6998.
- No licence information is recorded for this record.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
Photosynthetic water oxidation is catalyzed by the Mn<sub>4</sub>CaO<sub>5</sub> cluster of photosystem II (PSII) with linear progression through five S-state intermediates (S<sub>0</sub> to S<sub>4</sub>). To reveal the mechanism of water oxidation, we analyzed structures of PSII in the S<sub>1</sub>, S<sub>2</sub>, and S<sub>3</sub> states by x-ray free-electron laser serial crystallography. No insertion of water was found in S<sub>2</sub>, but flipping of D1 Glu<sup>189</sup> upon transition to S<sub>3</sub> leads to the opening of a water channel and provides a space for incorporation of an additional oxygen ligand, resulting in an open cubane Mn<sub>4</sub>CaO<sub>6</sub> cluster with an oxyl/oxo bridge. Structural changes of PSII between the different S states reveal cooperative action of substrate water access, proton release, and dioxygen formation in photosynthetic water oxidation.
Medical subject headings
- Oxygen
- Photosystem II Protein Complex
- Water