Nonribosomal peptide synthetases: structures and dynamics.

Nonribosomal peptide synthetases (NRPSs) are large multimodular biocatalysts that utilize complex regiospecific and stereospecific reactions to assemble structurally and functionally diverse peptides that have important medicinal applications. During this ribosome-independent peptide synthesis, catalytic domains of NRPS select, activate or modify the covalently tethered reaction intermediates to control the iterative chain elongation process and product release. Recent advances in structural elucidation of domains, didomains, and an entire termination module revealed valuable insights into the mechanism of nonribosomal synthesis and are highlighted herein.

Crystal structure of the termination module of a nonribosomal peptide synthetase.

Nonribosomal peptide synthetases (NRPSs) are modular multidomain enzymes that act as an assembly line to catalyze the biosynthesis of complex natural products. The crystal structure of the 144-kilodalton Bacillus subtilis termination module SrfA-C was solved at 2.6 angstrom resolution. The adenylation and condensation domains of SrfA-C associate closely to form a catalytic platform, with their active sites on the same side of the platform. The peptidyl carrier protein domain is flexibly tethered to this platform and thus can move with its substrate-loaded 4'-phosphopantetheine arm between the active site of the adenylation domain and the donor side of the condensation domain. The SrfA-C crystal structure has implications for the rational redesign of NRPSs as a means of producing novel bioactive peptides.