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.
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.
Corthésy
B E
BE
Département de Biochimie Médicale, Centre Médical Universitaire, Genève, Switzerland.
Wallace
C J
CJ
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis; D001120:Arginine / Q000378:metabolism*; D001665:Binding Sites / Q000187:drug effects; D002852:Chromatography, Ion Exchange; D003512:Cyclohexanones / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D004590:Electrophoresis, Paper; D010084:Oxidation-Reduction
D000596:Amino Acids; D003512:Cyclohexanones; D003574:Cytochrome c Group; C018031:1,2-cyclohexanedione; D000255:Adenosine Triphosphate; D001120:Arginine