RESONANCE RAMAN CHARACTERIZATION OF CHROMATIUM-VINOSUM CYTOCHROME-C' - EFFECT OF PH AND COMPARISON OF EQUILIBRIUM AND PHOTOLYZED CARBON-MONOXIDE SPECIES

Resonance Raman spectra of Chromatium vinosum cytochrome c′ have been obtained for the five pH-dependent states of the protein [i.e., types I (pH 7), II (pH 10), and III (pH 12) of the ferric protein and type a (pH 7) and type n (pH 12) of the ferrous protein]. The raman spectra of type II and type a are consistent with those of high-spin, 5-coordinate heme proteins, such as deoxyhemoglobin, while spectra of type III and type n correspond more closely to those of low-spin, ferric and ferrous cytochrome c, respectively. Spectra of the CO-bound equilibrium species qualitatively resemble those of carbon monoxy human HbA. However, both the Fe-C and C=O stretching modes of the ligated species exhibit pH-de-pendent frequency shifts. Our data also indicate that CO photolysis is much more efficient at pH 7 than at pH 12. Moreover, the spectra of the photolytic transients suggest that unique, high-spin species are formed subsequent to CO photolysis from both type a and type n species. © 1990, American Chemical Society. All rights reserved.