Jahnellamides, α-keto-β-methionine-containing peptides from the terrestrial myxobacterium Jahnella sp.: structure and...

Two new cyclic peptides, termed jahnellamides A and B, were isolated from the myxobacterium Jahnella sp. Their structures were solved by NMR, ESIMS, and chemical derivatizations. Jahnellamides are a new class of α-ketoamide-containing peptides comprised of nonproteinogenic amino acids, including α-keto-β-methionine and 4-hydroxyglutamic acid. Moreover, in silico analysis of the genome sequence along with feeding experiments allowed us to identify and annotate a candidate nonribosomal peptide synthetase biosynthetic gene cluster containing a polyketide synthase module involved in the formation of the α-ketoamide moiety.