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Biochim Biophys Acta. 2008 Jul-Aug;1777(7-8):890-2. doi: 10.1016/j.bbabio.2008.03.016. Epub 2008 Mar 29.

Prevention of leak in the proton pump of cytochrome c oxidase.

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Helsinki Bioenergetics Group, Structural Biology and Biophysics Programme, Institute of Biotechnology, University of Helsinki, PB 65 (Viikinkaari 1), 00014 University of Helsinki, Helsinki, Finland.


The cytochrome c oxidases (CcO), which are responsible for most O(2) consumption in biology, are also redox-linked proton pumps that effectively convert the free energy of O(2) reduction to an electrochemical proton gradient across mitochondrial and bacterial membranes. Recently, time-resolved measurements have elucidated the sequence of events in proton translocation, and shed light on the underlying molecular mechanisms. One crucial property of the proton pump mechanism has received less attention, viz. how proton leaks are avoided. Here, we will analyse this topic and demonstrate how the key proton-carrying residue Glu-242 (numbering according to the sequence of subunit I of bovine heart CcO) functions as a valve that has the effect of minimising back-leakage of the pumped proton.

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