Kinetics of proton pumping in cytochrome c oxidase

TL;DR

This paper presents a simplified kinetic model of cytochrome c oxidase that captures the timing and efficiency of proton pumping driven by electron transfer, aligning with experimental observations.

Contribution

It introduces a minimal model with four redox centers and protonable sites to simulate proton pumping kinetics and efficiency in cytochrome c oxidase.

Findings

Model reproduces all four kinetic phases observed experimentally.

Proton pumping efficiency depends on transmembrane voltage and temperature.

Efficient proton translocation can occur under realistic parameters.

Abstract

We propose a simple model of cytochrome c oxidase, including four redox centers and four protonable sites, to study the time evolution of electrostatically coupled electron and proton transfers initiated by the injection of a single electron into the enzyme. We derive a system of master equations for electron and proton state probabilities and show that an efficient pumping of protons across the membrane can be obtained for a reasonable set of parameters. All four experimentally observed kinetic phases appear naturally from our model. We also calculate the dependence of the pumping efficiency on the transmembrane voltage at different temperatures and discuss a possible mechanism of the redox-driven proton translocation.