Title: A kinetic model of proton transport in a multi-redox centre protein: cytochrome coxidase
Language: English
Authors: Srajer, Johannes
Schwaighofer, Andreas  
Hildenbrandt, David M. 
Kibrom, Asmorom 
Naumann, Renate L.C.
Category: Original Research Article
Issue Date: 2013
Journal: Progress in Reaction Kinetics and Mechanism
ISSN: 1471-406X
We use chemical reaction kinetics to explore the stepwise electron and proton transfer reactions of cytochrome c oxidase (CcO) from R. sphaeroides. Proton transport coupled to electron transport (ET) is investigated in terms of a sequence of protonation-dependent second-order redox reactions. Thereby, we assume fixed rather than shifting dissociation constants of the redox sites. Proton transport can thus be simulated particularly when separate proton uptake and release sites are assumed rather than the same proton pump site for every ET step. In order to test these assumptions, we make use of a model system introduced earlier, which allows us to study direct ET of redox enzymes by electrochemistry. A four-electron transfer model of CcO had been developed before, according to which electrons are transferred from the electrode to CuA. Thereafter, electrons are transferred along the sequence heme a, heme a3 and CuB. In the present investigation, we consider protonation equilibria of the oxidised and reduced species for each of the four centres. Moreover, we add oxygen/H2O as the terminal (fifth) redox couple including protonation of reduced oxygen to water. Finally we arrive at a kinetic model comprising five protonation-dependent redox couples. The results from the simulations are compared with experimental data obtained in the absence and presence of oxygen. As a result, we can show that proton transport can be modelled in terms of protonation-dependent redox kinetics.
Keywords: proton pump; protonation-dependent chemical reaction kinetics; second-order redox reaction; metalloprotein; master equation
DOI: 10.3184/146867812X13558465325118
Library ID: AC15520863
URN: urn:nbn:at:at-ubtuw:3-7625
Organisation: E164 - Institut für Chemische Technologien und Analytik 
Publication Type: Article
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