title: The modulation of cytochrome c electron self-exchange by site-specific chemical modification and anion binding.
abstract: The site-specific chemical modification of horse heart cytochrome c at Lys-13 and -72 using 4-chloro-3,5-dinitrobenzoic acid (CDNB) increases the electron self-exchange rate of the protein. In the presence of 0.24 M cacodylate (pH* 7.0) the electron self-exchange rate constants, kex, measured by a 1H NMR saturation transfer method at 300 K, are 600, 6 X 10(3) and 6 X 10(4) M-1 X s-1 for native, CDNP-K13 and CDNP-K72 cytochromes c respectively. Repulsive electrostatic interactions, which inhibit cytochrome c electron self-exchange, are differentially affected by modification. Measurements of 1H NMR line broadening observed with partially oxidised samples of native cytochrome c show that ATP and the redox inert multivalent anion Co(CN)3-6 catalyse electron self-exchange. At saturation a limiting value of approximately 1.4 X 10(5) M-1 X s-1 is observed for both anions.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000838:Anions; D002101:Cacodylic Acid / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D002723:Chlorobenzoates; D003035:Cobalt / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport / Q000187:drug effects; D008239:Lysine; D009682:Magnetic Resonance Spectroscopy
chemical_list: D000838:Anions; D002723:Chlorobenzoates; D003486:Cyanides; D003574:Cytochrome c Group; C015746:4-chloro-3,5-dinitrobenzoate; C027033:hexacyanocobaltate (III); D003035:Cobalt; D000255:Adenosine Triphosphate; D002101:Cacodylic Acid; D008239:Lysine