ISOLATION AND CHARACTERIZATION OF VIBRATIONAL-SPECTRA OF INDIVIDUAL HEME ACTIVE-SITES IN CYTOCHROME BC(1) COMPLEXES FROM RHODOBACTER-CAPSULATUS

Resonance Raman spectra of bc(1) complexes and isolated c(1) subunit f rom Rhodobacter capsulatus have been obtained using a variety of excit ation wavelengths. Spectra obtained via Q-band excitation of bc(1) com plexes in different redox states were separated to yield the individua l vibrational spectra of each of the three heme active sites, Hemes b( H) and c(1) exhibit vibrational spectra typical of b- and c-type hemes , respectively, In contrast, the spectrum of heme b(L) is anomalous wi th respect to those of other hemes b. The isolated spectra were also u sed to assess the effects of inhibitor binding on the local structural environments of the hemes. Neither antimycin nor myxothiazol binding produces dramatic structural perturbations at the hemes. Heme ct is co mpletely unaffected by the presence of either inhibitor. The vibration al spectra of hemes b(H) and b(L) are slightly altered by antimycin an d myxothiazol binding, respectively.