Widespread microbial utilization of ribosomal β-amino acid-containing peptides and proteins

Abstract

<h2>Summary</h2> β-Amino residues are regarded as extremely rare features among ribosomal products. They can be installed by a remarkable non-canonical enzymatic splicing process occurring in some Nif11-type ribosomally synthesized and posttranslationally modified peptide (RiPP) pathways from select cyanobacteria. The functions of the final pathway products remained unknown. Here, a global bioinformatic analysis suggested an unexpectedly broad distribution of ribosomal β-amino acid products in diverse bacterial lineages as well as archaea. Characterization of 27 bacterial splicease-substrate pairs confirmed the modification in all cases. The "spliceotide" products include many previously unrecognized RiPP types as well as proteins, contain 35 to >600 residues, and feature single to multiple α-keto-β-amino acid moieties, with 15 different naturally occurring β units characterized and 20 predicted. Of three tested spliceotides, all exhibited exceptionally potent protease inhibitory activity, providing a potential rationale for the widespread splicease chemistry in prokaryotes and highlighting substantial potential for drug discovery and gene-based biomolecule diversification.