No abstract

The putative protective role of the Nu-acetyl group of proteins has been investigated. Synthetic, non-acetylated Nterminal tetrapeptides of the aA2-and 711-crystallin chains are good substrates for leucine aminopeptidase, while the acetylated ones are completely resistant. In the native, non-acetylated, y-crystallin the N terminus is not degraded by leucine aminopeptidase. Newly synthesized aA2-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"-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.

No abstract