Pathways of Proton Transfer in Cytochrome c Oxidase |
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Authors: | Peter Brzezinski Pia Ädelroth |
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Institution: | (1) Department of Biochemistry and Biophysics, Göteborg University and Chalmers University of Technology, Medicinaregatan 9C, S-413 90 Göteborg, Sweden |
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Abstract: | During the last few years our knowledge of the structure and function of heme copper oxidases has greatly profited from the use of site-directed mutagenesis in combination with biophysical techniques. This, together with the recently-determined crystal structures of cytochrome c oxidase, has now made it possible to design experiments aimed at targeting specific pump mechanisms. Here, we summarize results from our recent kinetic studies of electron and proton-transfer reactions in wild-type and mutant forms of cytochrome c oxidase from Rhodobacter sphaeroides. These studies have made it possible to identify amino acid residues involved in proton transfer during specific reaction steps and provide a basis for discussion of mechanisms of electron and proton transfer in terminal oxidases. The results indicate that the pathway through K(I-362)/T(I-359), but not through D(I-132)/E(I-286), is used for proton transfer to a protonatable group interacting electrostatically with heme a
3, i.e., upon reduction of the binuclear center. The pathway through D(I-132)/E(I-286) is used for uptake of pumped and substrate protons during the pumping steps during O2 reduction. |
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Keywords: | Electron transfer flow-flash proton pumping cytochrome aa
3 flash photolysis |
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