title: Cobalt-cytochrome c. I. Preparation, properties, and enzymic activity.
abstract: An improved procedure for the preparation of cobalt-cytochrome c has been developed. Various factors influencing the cobalt insertion process are discussed. The optical spectra of cobalt-cytochrome c suggest a six-coordinated species. The spectral shifts occurring with oxidation-reduction are compared with those observed for deoxy-cobaltohemoglobin and ferrocytochrome c and attributed to the effect of d(z2) electron on stereoelectronic interactions between the axial ligands and the porphyrin pi systems. Cobalt-cytochrome c has Em,7 = -140 +/- 20 mV as compared to an Em,7 of +250mV for ferrocytochrome c. An explanation for this negative Em,7 is offered. Cobaltocytochrome c is oxidized by cytochrome oxidase at about 45% of the rate for native cytochrome c. On the other hand cobalticytochrome c was not reduced by microsomal NADH or NADPH cytochrome c reductase nor by mitochondrial NADH or succinate cytochrome c reductase. It appears that the integrity of the reductase binding site is destroyed and the oxidase binding site has been modified by cobalt substitution.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003035:Cobalt / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D003576:Electron Transport Complex IV; D006736:Horses; D008024:Ligands; D008433:Mathematics; D008931:Mitochondria, Muscle / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D011166:Porphyrins; D011485:Protein Binding; D011487:Protein Conformation; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D003574:Cytochrome c Group; D008024:Ligands; D011166:Porphyrins; D003035:Cobalt; D003576:Electron Transport Complex IV