Resonance Raman resolution of a-, b- and c-type cytochromes in membrane vesicles of alkalophilic bacteria.

Resonance Raman spectroscopy has been used to obtain complete spectra of each individual cytochrome type - a, b and c - in the reduced state within membrane vesicle preparations from two species of obligately alkalophilic bacteria: Bacillus alcalophilus and Bacillus firmus RAB. The vibrational spectra, in the range 250-1700 cm-1, were obtained with tunable dye laser excitation in the wavelength range 550-600 nm tuned to resonance with the appropriate reduced alpha band maximum for the cytochrome type of interest. The spectra reveal details which serve to characterize the specific type of cytochrome as well as to confirm the similarity of the heme prosthetic group to previously well-characterized cytochromes of the the a- b- or c-type. Preliminary evidence in support of heterogeneity of b-type, and possibly a-type cytochromes, or of heme-heme interaction within the membrane is presented.