Reactions of mitochondrial cytochrome c with iron-polyaminocarboxylate complexes

The binding of Fe(III)-polyaminocarboxylate (pac) complexes to mitochondrial ferricytochrome c and ferrocytochrome c has been studied by NMR and four binding sites on cytochrome c have been defined. These sites have different binding preferences for different pac complexes and these are not correlated with the kinetic classification of Wei and Ryan [J. Inorg. Biochem. 17, 237-246 (1982]. It is suggested that the classification of Wei and Ryan is faulty because an assumption made by these authors is incorrect. This assumption is that the reduction of ferricytochrome c by Fe(II)-(pac) complexes proceeds in all cases with similar electron transfer mechanisms with each of the pac complexes having similar self-exchange rates.