Change of Cytochrome c Structure during Development of the Mouse

The structure of cytochrome c during mouse development is investigated. For this purpose the amino acid sequence of cytochrome c of the adult mouse had to be determined. The structure of cytochrome c of adult differentiated mouse cells differs in two amino acid residues from the known amino acid sequence of rabbit cytochrome c. No indication of different forms of cytochrome c in the adult differentiated cells was obtained. The structure of cytochrome c from 11.5‐day‐old mouse embryos is identical with that of adult mouse tissues. Since germ cells after meiotic division are the immediate precursors of a new individual, the structure of cytochrome c from sperm‐containing mice testes was investigated. By means of chromatography of the cytochrome c and of peptide maps and amino acid analyses of its tryptic peptides, it is shown that mouse testis contains two isocytochromes c in about equal amount. The structure of one of these two isocytochromes c is identical with the structure of the adult‐type cytochrome c of mouse. The testis‐specific cytochrome c, which is assumed to be located in the sperm cells, differs in 13 of its 104 amino acid residues from the adult‐type cytochrome c. From comparison of the primary and the spatial structures of the adult‐type and the sperm‐type isocytochromes c with the known structures of cytochrome c of more than 65 different species it is concluded that the duplication of the cytochrome c structural gene, causing the existence of the two ontogenetic‐specific isocytochromes c in mouse, has occurred early in the evolution of eucaryotes.