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Proc Natl Acad Sci U S A. 2016 Jul 12;113(28):7810-5. doi: 10.1073/pnas.1608118113. Epub 2016 Jun 28.

Analyzing the electrogenicity of cytochrome c oxidase.

Author information

1
Department of Chemistry, University of Southern California, Los Angeles, CA 90089.
2
Department of Chemistry, University of Southern California, Los Angeles, CA 90089 warshel@usc.edu.

Abstract

Measurements of voltage changes in response to charge separation within membrane proteins can offer fundamental information on spectroscopically "invisible" steps. For example, results from studies of voltage changes associated with electron and proton transfer in cytochrome c oxidase could, in principle, be used to discriminate between different theoretical models describing the molecular mechanism of proton pumping. Earlier analyses of data from these measurements have been based on macroscopic considerations that may not allow for exploring the actual molecular mechanisms. Here, we have used a coarse-grained model describing the relation between observed voltage changes and specific charge-transfer reactions, which includes an explicit description of the membrane, the electrolytes, and the electrodes. The results from these calculations offer mechanistic insights at the molecular level. Our main conclusion is that previously assumed mechanistic evidence that was based on electrogenic measurements is not unique. However, the ability of our calculations to obtain reliable voltage changes means that we have a tool that can be used to describe a wide range of electrogenic charge transfers in channels and transporters, by combining voltage measurements with other experiments and simulations to analyze new mechanistic proposals.

KEYWORDS:

electrogenicity; electron transfer; membrane potential; proton transfer

PMID:
27357681
PMCID:
PMC4948359
DOI:
10.1073/pnas.1608118113
[Indexed for MEDLINE]
Free PMC Article

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