Imperial College London
Alternate

Professor Bill Rutherford FRS

Faculty of Natural Sciences, Department of Life Sciences

Chair in Biochemistry of Solar Energy
 
 
 
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Contact

 

+44 (0)20 7594 5329a.rutherford Website

 
 
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Location

 

702Sir Ernst Chain BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Fantuzzi:2022:10.1073/pnas.2116063119,
author = {Fantuzzi, A and Allgower, F and Baker, H and McGuire, G and Teh, WK and Gamiz-Hernandez, AP and Kaila, VRI and Rutherford, A},
doi = {10.1073/pnas.2116063119},
journal = {Proceedings of the National Academy of Sciences of USA},
title = {Bicarbonate-controlled reduction of oxygen by the QA semiquinone in Photosystem II in membranes},
url = {http://dx.doi.org/10.1073/pnas.2116063119},
volume = {119},
year = {2022}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Photosystem II (PSII), the water/plastoquinone photo-oxidoreductase, plays a key energy input role in the biosphere. Q−A, the reduced semiquinone form of the nonexchangeable quinone, is often considered capable of a side reaction with O2, forming superoxide, but this reaction has not yet been demonstrated experimentally. Here, using chlorophyll fluorescence in plant PSII membranes, we show that O2 does oxidize Q−A at physiological O2 concentrations with a t1/2 of 10 s. Superoxide is formed stoichiometrically, and the reaction kinetics are controlled by the accessibility of O2 to a binding site near Q−A, with an apparent dissociation constant of 70 ± 20 µM. Unexpectedly, Q−A could only reduce O2 when bicarbonate was absent from its binding site on the nonheme iron (Fe2+) and the addition of bicarbonate or formate blocked the O2-dependant decay of Q−A. These results, together with molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics calculations, indicate that electron transfer from Q−A to O2 occurs when the O2 is bound to the empty bicarbonate site on Fe2+. A protective role for bicarbonate in PSII was recently reported, involving long-lived Q−A triggering bicarbonate dissociation from Fe2+ [Brinkert et al., Proc. Natl. Acad. Sci. U.S.A. 113, 12144–12149 (2016)]. The present findings extend this mechanism by showing that bicarbonate release allows O2 to bind to Fe2+ and to oxidize Q−A. This could be beneficial by oxidizing Q−A and by producing superoxide, a chemical signal for the overreduced state of the electron transfer chain.
AU  - Fantuzzi,A
AU  - Allgower,F
AU  - Baker,H
AU  - McGuire,G
AU  - Teh,WK
AU  - Gamiz-Hernandez,AP
AU  - Kaila,VRI
AU  - Rutherford,A
DO  - 10.1073/pnas.2116063119
PY  - 2022///
SN  - 0027-8424
TI  - Bicarbonate-controlled reduction of oxygen by the QA semiquinone in Photosystem II in membranes
T2  - Proceedings of the National Academy of Sciences of USA
UR  - http://dx.doi.org/10.1073/pnas.2116063119
UR  - http://hdl.handle.net/10044/1/94240
VL  - 119
ER  -
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