The effect of complete or specific partial acetimidylation on the biological properties of cytochrome c and cytochrome c-T.

The biological consequences of acetimidylation of all 19 epsilon-amino groups of horse cytochrome c are a slight decrease in both the redox potential of the protein and its ability to stimulate oxygen uptake in the cytochrome c-depleted-mitochondria assay. Examination of a number of specific partially acetimidylated analogues and acetimidylated cytochromes c of other species has shown that the changes in biological properties, which are associated with a slight structural change as monitored by n.m.r. spectroscopy [Boswell, Moore, Williams, Harris, Wallace, Bocieck & Welti (1983) Biochem. J. 213, 679-686], appear to stem from modification of residues in a restricted region of the sequence. The failure of the redox potential of Saccharomyces cerevisae cytochrome c to be affected by acetimidylation suggests that it is lysine-53, absent from that species, that is the sensitive residue.