Biosynthetic Gene Cluster of Linaridin Peptides Contains Epimerase Gene

Abstract Salinipeptins belong to the type‐A linaridin class of ribosomally synthesized and post‐translationally modified peptides (RiPPs) comprising 22 amino acid residues with multiple D ‐amino acids. Although chirality of other type‐A linaridins, such as grisemycin and cypemycin, has not been reported, the biosynthetic gene clusters of type‐A linaridins have identical gene organization. Here, we report heterologous expression of grisemycin biosynthetic gene cluster ( grm ) and show that grisemycin contains multiple D ‐amino acids, similar to salinipeptins. The heterologous expression experiments also confirm the involvement of a novel peptide epimerase in grisemycin biosynthesis. Gene‐deletion experiments indicate that grmL , a single gene with unknown function, is indispensable for grisemycin production. We also show that the presence of D ‐amino acids is likely a common feature of linaridin natural products by analyzing two other type‐A linaridin clusters.