1H NMR Studies of the Electron Exchange Between Cytochrome c and Iron Hexacyanides

Binding of [Fe(CN)6]3−, [Cr(CN)6]3−, [Co(CN)6]3− and [Cr(C2O4)3]3− to horse, tuna and Candida krusi cytochromes c has been studied by high-resolution 1H NMR spectroscopy. All the reagents bind at the same sites. There are at least two binding sites, and probably three, on horse cytochrome c at pH 7. One of the sites is only a weak binding site and is far from the haem group, whereas the other site(s) is(are) at the haem crevice. Ka for binding of [Fe(CN)6]3− to trimethyllysine-72 of C. krusei ferricytochrome c is 140±15 M1 at 27 C and pH 7.