PEPTIDE SELF-REPLICATION VIA TEMPLATE-DIRECTED LIGATION

A 32-residue a-helical peptide with a sequence similiar to that of the GCN4 leucine zipper region is shown to catalyze its own formation by accelerating the amide bond formation of a 17-residue peptide, preacti vated as a thiobenzyl ester, and a 15-residue peptide with a N-termina l cysteine. The self-replication process displays parabolic growth cha racteristics as revealed by a detailed kinetic analysis. Control react ions with single-mutant peptides strongly support a mechanism in which a ternary and/or quaternary complex of the product with both peptide fragments act(s) as the catalytically active intermediate(s). Furtherm ore, these experiments reveal a remarkable sequence selectivity, as ev idenced by the loss of autocatalytic activity as a result of a single replacement of leucine or valine residues with an alanine at the recog nition interface.