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The oxidation-state-dependent ATP-binding site of cytochrome c. Implication of an essential arginine residue and the effect of occupancy on the oxidation-reduction potential.

ABSTRACT: Arg-91 is not part of the active site of cytochrome c that mediates binding and electron transfer, yet it is absolutely conserved in eukaryotic cytochromes c, indicating a special function. The physicochemical properties of analogues are unaffected by the modification of this residue, so they can be used with confidence to study the role of Arg-91. We have established limiting conditions under which this residue alone is specifically modified by cyclohexane-1,2-dione, and have subsequently shown that ATP, and to a lesser extent ADP or Pi, protects it from the action of the reagent in an oxidation-state-dependent manner. These observations strongly support the idea that this site exerts a controlling influence on cytochrome c activity in the electron transport or other cellular redox systems, and we have commenced a study of how that influence might operate. We find that the redox potentials of both cytochrome c and analogue are little affected by changing ATP or Pi concentrations.

SUBMITTER: Corthesy BE

PROVIDER: S-EPMC1149151 | biostudies-other | 1988 Jun

REPOSITORIES: biostudies-other

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Arginine-178 is an essential residue for ITPA function.

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