H-1 NMR-studies of heme iron coordination in cytochrome c-552 from euglena-gracilis Academic Article uri icon

publication date

  • 1977


  • The coordination of the heme iron in cytochrome c-552 from Euglena gracilis was investigated by 1H NMR studies at 360 MHz. The data imply that the axial heme ligands are His-14 and Met-56 in both the oxidized and the reduced protein. Studies of mixed solutions of ferro- and ferricytochrome c-552, which provided much of the information on the heme structure, also showed that the intermolecular electron exchange is characterized by a bimolecular rate constant of 5-10(6) mol-1-s-1 at 29 degrees C, which is three orders of magnitude faster than the corresponding reaction in solutions of mammalian cytochromes c.