Resonance Raman investigation of a soluble cytochrome c552 from alkaliphilic Bacillus firmus RAB.

Abstract The environment of the heme site of a low-potential soluble cytochrome ( c 552 ) from alkaliphilic Bacillus firmus RAB has been characterized with resonance Raman scattering and compared to that of horse heart cytochrome c . The Raman data indicate that vibrational bands sensitive to the axial ligation of the heme, as well as modes sensitive to the heme peripheral environment in cytochrome c 552 , are distinct from those of horse heart cytochrome c . The spectra of cytochrome c 552 display resonance Raman modes indicative of a methionine as the sixth ligand in the oxidized form, while the reduced form appears to contain a nitrogenous-based sixth ligand. In addition, Q-band excitation reveals differences among vibrational modes in cytochrome c 552 that are sensitive to the amino acid environment surrounding the heme.