1H-NMR studies of structural homologies between the heme environments in horse cytochrome c and in cytochrome c-552 from Euglena gracilis.

With the use of proton-proton Overhauser enhancement experiment the spatial arrangement relative to the heme group of amino acid side chains in the heme crevice of horse ferrocytochrome c and ferrocytochrome c-552 from euglena gracilis was investigated. From these data and the known crystal structure for mammalian cytochromes c, individual assignments were obtained for several aromatic residues in horse ferrocytochrome c. This then provided a basis for delineating homologies between the polypeptide conformations near the heme group in horse ferrocytochrome c and ferrocytochrome c-552, for which no crystal structure has as yet been described.