Lanthipeptides are ribosomally synthesized peptides which undergo extensive post-translational modifications. In addition to novel structural features and bioactivities, the in vitro study on the biosynthesis of the class III lanthipeptide labyrinthopeptin revealed a unique C- to N-terminal directionality of biosynthetic processing. The recently described class III lanthipeptide curvopeptin allowed investigating the directionality aspect in much greater detail: Structural characterization of nine curvopeptin biosynthesis intermediates by high-resolution mass spectrometry combined with a deuterium-labeling approach enabled for the first time building a comprehensive biosynthesis model featuring all three post-translational modification reactions: phosphorylation, elimination, and cyclization. These results point to a nonlinear processing scheme with a predominant C → N-terminal directionality. Our data give important mechanistic insights into the concerted processing and directionality of the multifunctional class III modifying enzymes. The data are of significance in the light of obtaining a mechanistic understanding of the post-translational biosynthesis machinery of the growing variety of ribosomally synthesized and post-translationally modified peptides.

Feglymycin, a peptide antibiotic produced by Streptomyces sp. DSM 11171, consists mostly of nonproteinogenic phenylglycine-type amino acids. It possesses antibacterial activity against methicillin-resistant Staphylococcus aureus strains and antiviral activity against HIV. Inhibition of the early steps of bacterial peptidoglycan synthesis indicated a mode of action different from those of other peptide antibiotics. Here we describe the identification and assignment of the feglymycin (feg) biosynthesis gene cluster, which codes for a 13-module nonribosomal peptide synthetase (NRPS) system. Inactivation of an NRPS gene and supplementation of a hydroxymandelate oxidase mutant with the amino acid l-Hpg proved the identity of the feg cluster. Feeding of Hpg-related unnatural amino acids was not successful. This characterization of the feg cluster is an important step to understanding the biosynthesis of this potent antibacterial peptide.

Phenylglycines are building blocks of many non-ribosomally synthesized peptides. The dihydroxyphenylglycine-containing cyclodepsipeptide cochinmicin I exhibits endothelin receptor antagonist activity. Therefore, it represents an interesting and synthetically challenging molecule because of the racemization-prone nature of dihydroxyphenylglycine. We present the total synthesis of cochinmicin I and the non-natural derivative cochinmicin VI and describe the identification and assignment of the cochinmicin (cmn) biosynthesis gene cluster, encoding a five-module non-ribosomal peptide synthetase for cochinmicin assembly.