Protonic sidedness of the binuclear iron‐copper centre in cytochrome oxidase

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Abstract
The oxidised (ferric-cupric) binuclear centre of cytochrome oxidase is converted into two other states, presumably ferryl-cupric (F) and ferric-peroxy-cupric (P), by energy-dependent reversed electron transfer from the centre (and water) to cytochrome c [(1981) Proc. Natl. Acad. Sci. USA 78, 4051–4054; (1987) Chem. Scr. 27B, 53–58]. This sequence of events represents a partial reversal of the O2 reduction catalysed by the centre. Here it is shown that the strong pH-dependence of these reactions is exerted specifically from the matrix (M) side of the inner mitochondrial membrane. This proves un-equivocally that the binuclear centre generates protonmotive force by means of its vectorial accessibility for electrons and protons