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The modulation of cytochrome c electron self‐exchange by site‐specific chemical modification and anion binding
Author(s) -
Concar David W.,
Hill H.Allen O.,
Moore Geoffrey R.,
Whitford David,
Williams Robert J.P.
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)81331-x
Subject(s) - cytochrome c , chemistry , electron transfer , cytochrome , electron transport chain , electron exchange , chemical modification , ion , redox , hemeprotein , stereochemistry , inorganic chemistry , crystallography , photochemistry , enzyme , organic chemistry , heme , biochemistry , mitochondrion
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, k ex , measured by a 1 H NMR saturation transfer method at 300 K, are 600, 6 × 10 3 and 6 × 10 4 M −1 ·s −1 for native, CDNP‐K13 and CDNP‐K72 cytochromes c respectively. Repulsive electrostatic interactions, which inhibit cytochrome c electron selfexchange, are differentially affected by modification. Measurements of 1 H NMR line broadening observed with partially oxidised samples of native cytochrome c show that ATP and the redox inert multivalent anion Co(CN) 6 3− catalyse electron self‐exchange. At saturation a limiting value of ~ 1.4 × 10 5 M −1 ·s −1 is observed for both anions.