Fourier-transform infra-red studies of the alkaline isomerization of mitochondrial cytochrome c and the ionization of carboxylic acids

The alkaline transitions of tuna and horse ferricytochromes c and the trifluoroacetyl-lysine derivative of horse ferricytochrome c have been studied by Fourier-transform (FT) i.r. spectroscopy. The spectral perturbations resulting from the transition have been interpreted by reference to FT i.r. data on simple carboxylic-acid-containing compounds and a bacterial cytochrome c₅₅₁ in which a haem propionate ionizes without causing a significant conformational change. The analysis strongly suggests that ionization of a haem propionate of mitochondrial cytochrome c triggers the alkaline conformation change.