THE PRIMARY STRUCTURE OF THE CYTOCHROMEcFROM VARIOUS ORGANS OF THE HOG

Abstract

The amino acid sequence of hog heart cytochrome c was determined. Like the horse and human heart proteins it was found to consist of a single polypeptide chain 104 residues long with a N-acetylated amino-terminal residue. It differs from horse heart cytochrome c in only three positions, carrying serine instead of threonine at residue 47, glycine instead of lysine at residue 60, and glycine instead of threonine at residue 89. Methods are described for the preparation of cytochrome c, in good yield, from hog liver, kidney, brain, and skeletal muscle. These proteins were all shown to have primary structures identical with that of hog heart cytochrome c, indicating that, notwithstanding differences in the functional activities and embryological origins of the various tissues examined, there is no corresponding change in the structure of cytochrome c. It thus appears likely that the synthesis of all, or at least the bulk, of the cytochrome c is controlled by a single structural gene throughout the body. Minor molecular variants of the protein, which could have been detected at concentrations of 2 to 3% of the entire preparations, were not observed.