Effect of Enzymatic Methylation on the Import of in Vitro Synthesized Apocytochrome C into Mitochondria

Little more than a dozen protein posttranslational side-chain modification reactions have been identified. One such reaction, protein methylation, occurs ubiquitously in nature, in organisms ranging from prokaryotic to eukaryotic. The reaction involves N-methylation of lysine, arginine, histidine, alanine, proline and glutamine, O-methylesterifi-cation of glutamic and aspartic acid, and S-methylation of cysteine and methionine (1–3).