A trans-Acting Cyclase Offloading Strategy for Nonribosomal Peptide Synthetases

Area of Science:

• Biochemistry
• Molecular Biology
• Synthetic Biology

Background:

• Nonribosomal peptides are synthesized by large enzyme complexes called nonribosomal peptide synthetases (NRPSs).
• The final step typically involves thioesterases releasing or cyclizing the peptide from the NRPS assembly line.
• Surugamide biosynthesis involves two NRPS systems producing a cyclic (A) and a linear (F) peptide, both lacking terminal thioesterases.

Purpose of the Study:

• To investigate the mechanism of peptide release and cyclization in surugamide biosynthesis, given the absence of terminal thioesterases.
• To identify and characterize the enzyme responsible for the terminal processing of surugamides.

Main Methods:

• In vivo characterization of a β-lactamase superfamily cyclase.
• In vitro verification using a thioester mimic of linear surugamide A.
• Bioinformatic analysis of NRPS systems in filamentous Actinobacteria.

Main Results:

• A trans-acting cyclase was identified as the release factor for both surugamide A and surugamide F.
• The cyclase functions in both releasing the linear peptide and facilitating macrocyclization.
• Bioinformatics suggests approximately 11% of filamentous Actinobacteria utilize such trans-acting cyclases instead of embedded thioesterases.

Conclusions:

• This work uncovers a novel pathway for nonribosomal peptide release and cyclization, expanding the known NRPS mechanisms.
• The findings provide a new tool for synthetic biology applications involving NRPS-derived compounds.
• The study highlights the diversity of NRPS terminal processing strategies in nature.