Structure of Yeast Cytochrome c

II. Proteinase Digestion and Ultraviolet Difference Spectra

Abstract

1. Saccharomyces oviformis M₂ cytochrome c, sulfhydryl type or non-sulfhydryl type were digested by proteinases, and non-sulfhydryl type cytochrome c was digested much faster than sulfhydryl types.
2. The difference spectra of urea treated and untreated cytochrome c were examined for sulfhydryl type group or non-sulfhydryl type group. The absolute value of ΔA at minima in the difference spectra obtained from sulfhydryl type cytochrome c were smaller than the non-sulfhydryl type cyto-chrome c. These results coincide with the results of the proteinase digestion.
3. The changes of the proteinase digestability and of ultraviolet difference spectra with urea treatment were reversible. And the three types of cytochrome c of Saccharo-myces oviformis M₂ (sulfhydryl, disulfide, and thiosulfate type) were freely interconverted into each other. The conformation of cyto-chrome c in its sulfhydryl type was rather rigid, but the conformation was converted to a loose form when any reagents (including sulfhydryl type cytochrome c itself) were combined to this sulfhydryl group.