Photophysical properties of cytochromes c-553 and c3 extracted from Desulfovibrio vulgaris Miyazaki

Abstract

Fluorescence and UV/visible absorption properties were studied on electron carrier proteins cytochromes c-553 and c 3 and their Fe-free forms (Fe-free cytochromes) over wide pH and temperature ranges in comparison with cytochrome c, hemin and microperoxidase-9 (MP-9). Although cytochromes c-553 and c 3 were extracted from the same sulfate-reducing bacterium, their absorption spectra at acidic pH and pH dependence of fluorescence spectra were different. Cytochrome c-553 showed photophysical characteristics similar to cytochrome c. This is attributed to the influence of the ligands of the fifth and sixth positions of the heme iron in cytochromes c-553 and c 3, which was confirmed by the experiments on MP-9. Through the temperature-dependent fluorescence spectrum and time profile, the coexistence of protonated and deprotonated forms of Fe-free cytochromes at neutral pH was observed. The fluorescence in native cytochromes was observed at acidic pH, whereas MP-9 and hemin showed no fluorescence at the same condition.