Discovery and Characterization of Bicereucin, an Unusual d -Amino Acid-Containing Mixed Two-Component Lantibiotic

Lantibiotics are a group of ribosomally synthesized and post-translationally modified peptides (RiPPs) exhibiting antimicrobial activity. They are characterized by the presence of the thioether-containing bisamino acids lanthionine and methyllanthionine. Here, we report a two-component lantibiotic from Bacillus cereus SJ1 with unusual structural features that we named bicereucin. Unlike all previous two-component lantibiotics, only one of the two peptides of bicereucin contains a lanthionine. The second peptide lacks any cysteines but contains several d-amino acids. These are installed by the dehydrogenase BsjJ_B, the activity of which was successfully reconstituted in vitro. The proteolytic removal of the leader peptide was also performed in vitro. Bicereucin displayed synergistic antimicrobial activities against Gram-positive strains including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci as well as hemolytic activity. To illustrate the utility of the enzymes, an analog of the d-amino acid containing opioid dermorphin was successfully produced in E. coli by employing the dehydratase BsjM and the dehydrogenase NpnJ_A.