An Acetyltransferase Conferring Self-Resistance of the Producer to Lasso Peptide Antibiotic Lariocidin

The soil microbiome, a reservoir of antibiotic-producing
bacteria,
also harbors resistance determinants encoded within antibiotic biosynthetic
gene clusters (BGCs). Studying self-resistance mechanisms, which have
evolved in producers to protect against their own toxic metabolites,
provides critical insights into the evolution of resistance and the
potential vulnerabilities of new antibiotics and can facilitate the
production of natural products in heterologous hosts. Here, we describe
the self-resistance mechanism to lariocidin (LAR), a recently discovered
lasso peptide antibiotic that inhibits the ribosomal machinery and
exhibits antibacterial activity against key pathogens. We identified
and characterized an N-acetyltransferase enzyme (LrcE)
encoded within the LAR BGC that mediates self-resistance in LAR-producing Paenibacillus sp. M2. LrcE is a member of the GCN5-related N-acetyltransferase (GNAT) superfamily and performs site-specific
acetylation of LAR at a critical lysine residue. This modification
disrupts ribosomal binding, thereby reducing LAR’s antibacterial
activity. Using in silico modeling, we predicted a conserved acetyl-CoA-binding
motif and an LAR-binding region on LrcE. Bioinformatic analysis revealed
LrcE homologues in environmental but not clinically relevant pathogens,
suggesting a limited risk of horizontal gene transfer and, therefore,
supporting the further development of LAR as a next-generation antibiotic.