Abstract
A study is presented of co-operative redox-linked protolytic reactions (redox Bohr effects) in soluble cytochrome- c oxidase purified from bovine-heart mitochondria. Bohr effects were analyzed by direct measurement, with accurate spectrophotometric and potentiometric methods, of H + uptake and release by the oxidase associated with reduction and oxidation of hemes a and a 3, Cu A and Cu B in the unliganded and in the CN- or CO-liganded enzyme. The results show that there are in the bovine oxidase four protolytic groups undergoing reversible p K shifts upon oxido-reduction of the electron transfer metals. Two groups with p K ox and p K red values around 7 and >12 respectively appear to be linked to redox transitions of heme a 3. One group with p K ox and p K red around 6 and 7 is apparently linked to Cu B, a fourth one with p K ox and p K red of 6 and 9 appears to be linked to heme a. The possible nature of the amino acids involved in the redox Bohr effects and their role in H + translocation is discussed.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Bioenergetics
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