Post-translational peptide bond formation during concanavalin A processing in vitro

Abstract

Post-translational processing of concanavalin A (Con A) is complex, involving deglycosylation, proteolytic cleavage on the carboxy group side of asparagine residues and formation of a peptide bond de novo. This has been studied with the 125I-labelled Con A glycoprotein precursor as a substrate for processing in vitro. Extracts of immature jackbean cotyledons and the commercially available purified preparation of asparaginylendopeptidase were able to catalyse the above processes. The processing resulted in the conversion of the 33.5 kDa inactive glycoprotein precursor into an active lectin. Processing activity was maximal at approx. pH 5.5. Evidence to support processing at authentic sites was obtained by observation of the release of 125I at positions in the sequence where tyrosine residues were present.