| Autor: |
Allgöwer F; Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden., Gamiz-Hernandez AP; Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden., Rutherford AW; Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom., Kaila VRI; Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden. |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2022 Apr 27; Vol. 144 (16), pp. 7171-7180. Date of Electronic Publication: 2022 Apr 14. |
| DOI: |
10.1021/jacs.1c13041 |
| Abstrakt: |
Photosystem II (PSII) catalyzes light-driven water oxidization, releasing O 2 into the atmosphere and transferring the electrons for the synthesis of biomass. However, despite decades of structural and functional studies, the water oxidation mechanism of PSII has remained puzzling and a major challenge for modern chemical research. Here, we show that PSII catalyzes redox-triggered proton transfer between its oxygen-evolving Mn 4 O 5 Ca cluster and a nearby cluster of conserved buried ion-pairs, which are connected to the bulk solvent via a proton pathway. By using multi-scale quantum and classical simulations, we find that oxidation of a redox-active Tyr z (Tyr161) lowers the reaction barrier for the water-mediated proton transfer from a Ca 2+ -bound water molecule (W3) to Asp61 via conformational changes in a nearby ion-pair (Asp61/Lys317). Deprotonation of this W3 substrate water triggers its migration toward Mn1 to a position identified in recent X-ray free-electron laser (XFEL) experiments [Ibrahim et al. Proc. Natl. Acad. Sci. USA 2020, 117, 12,624-12,635]. Further oxidation of the Mn 4 O 5 Ca cluster lowers the proton transfer barrier through the water ligand sphere of the Mn 4 O 5 Ca cluster to Asp61 via a similar ion-pair dissociation process, while the resulting Mn-bound oxo/oxyl species leads to O 2 formation by a radical coupling mechanism. The proposed redox-coupled protonation mechanism shows a striking resemblance to functional motifs in other enzymes involved in biological energy conversion, with an interplay between hydration changes, ion-pair dynamics, and electric fields that modulate the catalytic barriers. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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