Biosynthesis of Gut-Microbiota-Derived Lantibiotics Reveals a Subgroup of S8 Family Proteases for Class III Leader Removal.

Lanthipeptides are a group of ribosomally synthesized and post-translationally modified peptides with diverse structural features and bioactivities. Gut-microbiota-derived lanthipeptides play important roles in gut homeostasis of the host. Herein, we report the discovery and biosynthesis of class III lantibiotics named amylopeptins, which are derived from the gut microbiota of Sprague-Dawley rats and display a narrow antimicrobial spectrum. In contrast to known class III lanthipeptides, the biosynthesis of amylopeptins employs AmyP, which belongs to a subgroup of S8 family serine proteases, to remove the leader of corresponding precursor peptides in a site-specific manner during the last step of their maturation. Overall, this study shows for the first time that S8 family proteases participate in the biosynthesis of class III lanthipeptides.

Substrate plasticity of dehydratase SpaKC from the biosynthesis of thiosparsoamide.

Thioamitides are a group of ribosomally synthesized and post-translationally modified peptides that possess diverse bioactivities and are usually featured by thioamide and 2-aminovinyl-cysteine (AviCys) motifs. In natural product thiosparsoamide, the AviCys motif is formed by an enzyme cascade formed by the flavin-dependent decarboxylase SpaD and dehydratase SpaKC. SpaKC is a lanthipeptide synthetase homolog located outside the thiosparsoamide biosynthetic gene cluster. In this study, we show that SpaKC does not strictly require the N-terminal leader peptide of precursor peptide SpaA for substrate recognition and dehydration. The C-terminal seven residues serve as a minimal structural element for enzyme recognition. Through a systematic mutagenesis experiments, our study demonstrates the relaxed substrate specificity of SpaKC as a dehydratase and potentially as an enzymatic tool to install dehydroalanine or dehydrobutyrine motifs in peptides.