Peptide macrocyclization by a bifunctional endoprotease

Kalia Bernath-Levin, C. Nelson, A.G. Elliott, A.S. Jayasena, Harvey Millar, D.J. Craik, Josh Mylne

Research output: Contribution to journalArticle

45 Citations (Scopus)


© 2015 Elsevier Ltd. All rights reserved. Proteases usually cleave peptides, but under some conditions, they can ligate them. Seeds of the common sunflower contain the 14-residue, backbone-macrocyclic peptide sunflower trypsin inhibitor 1 (SFTI-1) whose maturation from its precursor has a genetic requirement for asparaginyl endopeptidase (AEP). To provide more direct evidence, we developed an in situ assay and used 18O-water to demonstrate that SFTI-1 is excised and simultaneously macrocyclized from its linear precursor. The reaction is inefficient in situ, but a newfound breakdown pathway can mask this inefficiency by reducing the internal disulfide bridge of any acyclic-SFTI to thiols before degrading it. To confirm AEP can directly perform the excision/ligation, we produced several recombinant plant AEPs in E. coli, and one from jack bean could catalyze both a typical cleavage reaction and cleavage-dependent, intramolecular transpeptidation to create SFTI-1. We propose that the evolution of ligating endoproteases enables plants like sunflower and jack bean to stabilize bioactive peptides.
Original languageEnglish
Pages (from-to)571-582
JournalChemistry and Biology
Issue number5
Publication statusPublished - May 2015

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