Methionine-Containing Rhabdopeptide/Xenortide-like Peptides from Heterologous Expression of the Biosynthetic Gene Cluster kj12ABC in Escherichia coli.

Seven new methionine-containing rhabdopeptide/xenortide-like peptides (1-7) were identified from Escherichia coli expressing the rhabdopeptide/xenortide-like peptide biosynthetic gene cluster kj12ABC from Xenorhabdus KJ12.1. Their structures were elucidated by detailed HPLC-HR-MS/MS analysis and confirmed by chemical synthesis. Bioactivity tests of these first rhabdopeptide/xenortide-like peptide derivatives (2-7) showing methionine building blocks compared to the usually found derivatives containing exclusively hydrophobic amino acids such as valine, leucine, or phenylalanine revealed good activities of 2-7 against protozoan parasites and no cytotoxicity against mammalian L6 cells.