High yield synthesis of cyclic analogues of antibacterial peptides P-113 by Sortase A-mediated ligation and their conformation studies

Abstract

P-113 is a fragment of natural occurring peptide Histatin 5 found in human saliva. This peptide exhibited broad spectrum of antibacterial and antifungal biological activities. In this study, bifunctional P-113 peptides 2–5 were designed as Sortase A substrates and synthesized by solid support peptide synthesis, where the N-terminus were equipped with glycine and its analogues, and C-terminus were extended with LPETGGS, respectively. Under Sortase A catalyzed condition, head to tail cyclization products 7–10 were afforded in yields from 76% to 93%. The conformation insights of linear peptides 2–5 and cyclic analogues 7–10 in aqueous buffers and in trifluroethanol (TFE) analyzed by circular dichroism (CD) suggested that α-helix structures were produced progressively in hydrophobic environment independent of the cyclization, which displayed the similar behavior as parent peptide P-113.