Download MendeleyDistal peptide elongation by a protease-like ligase and two distinct carrier proteins.
Gude, F., Bohne, A., Dell, M., Franke, J., Dunbar, K.L., Groll, M., Hertweck, C.(2026) Chem 12: None-None
- PubMed: 41641319
- DOI: https://doi.org/10.1016/j.chempr.2025.102740
- Primary Citation of Related Structures:
9QUZ, 9QVJ, 9QVK, 9QVL, 9QVO, 9QVP, 9QVQ, 9QVR, 9QVS - PubMed Abstract:
Closthioamide (CTA) is a potent antibiotic with a unique polythioamide scaffold produced by Ruminiclostridium cellulolyticum . Unlike classical non-ribosomal peptide synthetases (NRPSs), which use modular adenylation and condensation domains, CTA biosynthesis proceeds through non-canonical standalone enzymes. Central to this process is the papain-like ligase CtaG, which catalyzes amide bond formation between two distinct peptidyl carrier proteins (PCPs): CtaH, presenting para-hydroxybenzoic acid (PHBA), and CtaE, carrying a tri-β-alanine ((βAla) 3 ) chain. Using biochemical assays, chemical probes, crystallography, and mutational analysis, we show that CtaG operates via a ping-pong mechanism involving an enzyme-bound intermediate. A single substrate tunnel mediates directional transfer, enabling distal chain elongation that mirrors solid-phase peptide synthesis. Structure-based genome mining revealed homologous enzymes in the biosynthetic pathways of petrobactin, butirosin, and methylolanthanin. Together, our findings uncover a previously overlooked class of thiotemplated ligases and provide a mechanistic blueprint for engineering ribosome-independent peptide assembly lines.
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (Leibniz-HKI), 07743 Jena, Germany.
Organizational Affiliation:
