Co-opting the bacterial lipoprotein pathway in the biosynthesis of a lipidated macrocyclic peptide

A family of bacterial multinuclear non-heme iron dependent oxidative enzymes (MNIOs) are involved in diverse transformations during the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs). ChrH from the genus Chryseobacterium catalyzes a remarkable backbone rearrangement that involves macrocyclization, heterocyclization, and S-methylation. ChrH is part of a larger subfamily that includes members from other bacterial phyla. By leveraging comparative genomics, we characterize other products produced by this enzyme subfamily, which includes unmethylated macrocyclic congeners as well as C-terminally modified proteins of >30 kDa. We show that this MNIO subfamily recognizes substrates by their conserved C-terminal motif, allowing for structural diversification at their N-termini. For instance, the N-termini of some substrates contain a signal peptide for downstream maturation by the ubiquitous bacterial lipoprotein biosynthetic pathway. We demonstrate that, like bacterial lipoproteins, such peptides are modified by addition of diacylglycerol (DAG) groups to the N-terminal Cys residue along with acylation of the N-terminal amino group. Genome mining reveals examples of additional predicted RiPP-lipoprotein hybrids, which we term DAG-RiPPs. These results lay the foundation for the discovery of other RiPP-lipoproteins hybrids.