DOI: 10.1073/pnas.0608794104. Exploring the proton pump mechanism of cytochrome <i>c</i> oxidase in real time

Exploring the proton pump mechanism of cytochrome c oxidase in real time

10.1073/pnas.0608794104

Crossref journal-article

Proceedings of the National Academy of Sciences

Proceedings of the National Academy of Sciences (341)

Abstract

Cytochrome c oxidase catalyzes most of the biological oxygen consumption on Earth, a process responsible for energy supply in aerobic organisms. This remarkable membrane-bound enzyme also converts free energy from O 2 reduction to an electrochemical proton gradient by functioning as a redox-linked proton pump. Although the structures of several oxidases are known, the molecular mechanism of redox-linked proton translocation has remained elusive. Here, correlated internal electron and proton transfer reactions were tracked in real time by spectroscopic and electrometric techniques after laser-activated electron injection into the oxidized enzyme. The observed kinetics establish the long-sought reaction sequence of the proton pump mechanism and describe some of its thermodynamic properties. The 10-μs electron transfer to heme a raises the pK a of a “pump site,” which is loaded by a proton from the inside of the membrane in 150 μs. This loading increases the redox potentials of both hemes a and a 3 , which allows electron equilibration between them at the same rate. Then, in 0.8 ms, another proton is transferred from the inside to the heme a 3 /Cu B center, and the electron is transferred to Cu B . Finally, in 2.6 ms, the preloaded proton is released from the pump site to the opposite side of the membrane.

Bibliography

Belevich, I., Bloch, D. A., Belevich, N., WikstrÃ¶m, M., & Verkhovsky, M. I. (2007). Exploring the proton pump mechanism of cytochrome c oxidase in real time. Proceedings of the National Academy of Sciences, 104(8), 2685â2690.

Authors 5

Ilya Belevich (first)
Dmitry A. Bloch (additional)
Nikolai Belevich (additional)
Mårten Wikström (additional)
Michael I. Verkhovsky (additional)

References 45 Referenced 199

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Dates

Type	When
Created	18 years, 6 months ago (Feb. 9, 2007, 8:54 p.m.)
Deposited	3 years, 4 months ago (April 12, 2022, 2:36 p.m.)
Indexed	2 months ago (June 30, 2025, 1:05 a.m.)
Issued	18 years, 6 months ago (Feb. 20, 2007)
Published	18 years, 6 months ago (Feb. 20, 2007)
Published Online	18 years, 6 months ago (Feb. 20, 2007)
Published Print	18 years, 6 months ago (Feb. 20, 2007)

Funders 0

None

BibTeX

@article{Belevich_2007, title={Exploring the proton pump mechanism of cytochrome c oxidase in real time}, volume={104}, ISSN={1091-6490}, url={http://dx.doi.org/10.1073/pnas.0608794104}, DOI={10.1073/pnas.0608794104}, number={8}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Belevich, Ilya and Bloch, Dmitry A. and Belevich, Nikolai and Wikström, Mårten and Verkhovsky, Michael I.}, year={2007}, month=feb, pages={2685–2690} }

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  "abstract": "<jats:p>\n            Cytochrome\n            <jats:italic>c</jats:italic>\n            oxidase catalyzes most of the biological oxygen consumption on Earth, a process responsible for energy supply in aerobic organisms. This remarkable membrane-bound enzyme also converts free energy from O\n            <jats:sub>2</jats:sub>\n            reduction to an electrochemical proton gradient by functioning as a redox-linked proton pump. Although the structures of several oxidases are known, the molecular mechanism of redox-linked proton translocation has remained elusive. Here, correlated internal electron and proton transfer reactions were tracked in real time by spectroscopic and electrometric techniques after laser-activated electron injection into the oxidized enzyme. The observed kinetics establish the long-sought reaction sequence of the proton pump mechanism and describe some of its thermodynamic properties. The 10-\u03bcs electron transfer to heme\n            <jats:italic>a</jats:italic>\n            raises the pK\n            <jats:sub>a</jats:sub>\n            of a \u201cpump site,\u201d which is loaded by a proton from the inside of the membrane in 150 \u03bcs. This loading increases the redox potentials of both hemes\n            <jats:italic>a</jats:italic>\n            and\n            <jats:italic>a</jats:italic>\n            <jats:sub>3</jats:sub>\n            , which allows electron equilibration between them at the same rate. Then, in 0.8 ms, another proton is transferred from the inside to the heme\n            <jats:italic>a</jats:italic>\n            <jats:sub>3</jats:sub>\n            /Cu\n            <jats:sub>B</jats:sub>\n            center, and the electron is transferred to Cu\n            <jats:sub>B</jats:sub>\n            . Finally, in 2.6 ms, the preloaded proton is released from the pump site to the opposite side of the membrane.\n          </jats:p>",
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