Translocation mechanism, proton conductance

However, the details of the molecular mechanism of redox-linked proton translocation are still largely unknown, not only for cytochrome oxidase but for the entire respiratory chain. In considering various possibilities it is important to distinguish between basically different elementary steps of the process. Proton conduction through the protein is but one such element. Several possible mechanisms have been proposed for this function, based on conduction along hydrogen-bonded networks of amino acid residues within the membrane (reviewed in Ref. 8). In redox-linked... 

Figure 4. Leakage vs, conduction models for the permeation of protons. Left transient water wires form very infrequently in the nonpolar environment provided by lipid bilayers, but when they do, they could translocate just one proton very rapidly before breaking up only the hop step ofGrotthuss takes place. Right in polar channels such as GA, water wires are much more long-lived, which is consistent with their rapid relay of proton via a complete Grotthuss mechanism involving both hop and turn steps (l(f s ).

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