Redox-linked protolytic reactions in soluble cytochrome-c oxidase from beef-heart mitochondria: redox Bohr effects.
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 a3. CuA and CuB 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 pK shifts upon oxido-reduction of the electron transfer metals. Two groups with pKox and pKred values around 7 and > 12 respectively appear to be linked to redox transitions of heme a3. One group with pKox and pKred around 6 and 7 is apparently linked to CuB, a fourth one with pKox and pKred 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.
Capitanio
N
N
Institute of Medical Biochemistry and Chemistry, University of Bari, Italy.
Vygodina
T V
TV
Capitanio
G
G
Konstantinov
A A
AA
Nicholls
P
P
Papa
S
S
D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008929:Mitochondria, Heart / Q000201:enzymology*; D010084:Oxidation-Reduction; D017494:Proton Pumps / Q000378:metabolism; D012995:Solubility
D008024:Ligands; D017494:Proton Pumps; D003576:Electron Transport Complex IV; D010450:Endopeptidases