Ultrafast haem–haem electron transfer in cytochrome c oxidase

AbstractElectron transfer between the redox centres is essential for the function of the haem–copper oxidases. To date, the fastest rate of electron transfer between the haem groups has been determined to be ca. 3×105 s−1. Here, we show by optical spectroscopy that about one half of this electron transfer actually occurs at least three orders of magnitude faster, after photolysis of carbon monoxide from the half-reduced bovine heart enzyme. We ascribe this to the true haem–haem electron tunnelling rate between the haem groups