The function of N alpha-acetylation of the eye-lens crystallins.
The putative protective role of the N alpha-acetyl group of proteins has been investigated. Synthetic, non-acetylated N-terminal tetrapeptides of the alpha A2- and gamma II-crystallin chains are good substrates for leucine aminopeptidase, while the acetylated ones are completely resistant. In the native, non-acetylated, gamma-crystallin the N terminus is not degraded by leucine aminopeptidase. Newly synthesized alpha A2-crystallin, in which the normally occurring N-terminal acetylation has been prevented during cell-free translation, is virtually resistant against degradation by leucine aminopeptidase. Only at extreme enzyme-substrate ratios the N-terminal methionine is removed. Although the N alpha-acetyl group by its very nature protects against this exopeptidase, we conclude that the group is not essential for this purpose in the native crystallins.
D000123:Acetyltransferases / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002474:Cell-Free System; D003459:Crystallins / Q000378:metabolism*; D007908:Lens, Crystalline / Q000201:enzymology*; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D011817:Rabbits; D013379:Substrate Specificity
D003459:Crystallins; D000123:Acetyltransferases; D007931:Leucyl Aminopeptidase