Abstract
An improved device for potentiometry using magnetic circular dichroism spectroscopy has been developed and used to characterize the potentiometric behavior of solubilized beef heart cytochrome oxidase. In the absence of inhibitors, the electron affinity of cytochromes alpha and alpha 3 are indistinguishable and adequately described by the allosteric model of Nicholls and Peterson (Nicholls, P., and Peterson, L. C. (1972) Biochim. Biophys. Acta 357, 462-467). All of the cytochrome alpha can be accounted for as low spin heme throughout the titration. Cytochrome c present at 1:1, 2:1, and 4:1 stoichiometry with cytochrome alpha did not significantly affect the potentiometric behavior of alpha or chondroitinase alpha 3; at the 1:1 ratio the midpoint potential of cytochrome c was lowered by about 30 mV. In the presence of formate, azide and cyanide cytochrome alpha assumed approximately n = 1 behavior. However, the response of alpha 3 differed with each reagent and was particularly complex in the presence of azide. Fluoride produced very small changes in the potentiometric behavior suggesting that it may not be a ligand to cytochrome alpha 3. Possible deficiencies in the allosteric model are examined.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call