Novel two-part lantibiotic identified

Lantibiotics are polypeptide antibiotics that feature one or more thioether-linked ring substructures. They form when bacteria modify a precursor polypeptide by dehy­drating serine or threonine residues, followed by cyclizing them with a cysteine thiol. This process forms the amino acid lanthionine or methyllanthionine, which makes up one side of the ring (shown). A newly identified lantibiotic, dubbed bicereucin, is unusual in that it features two separate polypeptides that work in tandem to kill bacterial strains such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, report Liujie Huo and Wilfred A. van der Donk of the University of Illinois, Urbana-Champaign (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b02513). Working with Bacillus cereus strain SJ1, Huo and van der Donk identified the two bicereucin polypeptides, which they call Bsjα and Bsjβ. Bsjα lacks thioether-connected rings and consequently is not a lantibiotic, whereas Bsjβ is a traditional lantibiotic with one thioether ring. The researchers found that Bsjα appears to bind first to a target on a bacterium surface, and then Bsjβ binds to the bacterium-Bsjα complex. Only when both Bsjα and Bsjβ are present do they have antibiotic activity. The enzymes that process bicereucin may also be useful for producing d-amino-acid-containing polypeptides in synthetic biology applications, the researchers note.