Production of subtilosin A in E. coli: insights into the head-to-tail macrocyclization

Subtilosin A is the canonical member of the sactipeptide family with significant antimicrobial properties. In this study, we successfully produced subtilosin A in Escherichia coli by coexpressing the precursor peptide SboA with the radical SAM enzyme AlbA, and the metalloenzymes AlbE and AlbF. Our findings demonstrate that both AlbE and AlbF are essential for the head-to-tail macrocyclization of subtilosin A. We also identified an open-chain analog of subtilosin A, subtilosin A_OC, which retains the thioether crosslinks but lacks the macrocyclic structure. Subtilosin A_OC is likely a biosynthetic intermediate of subtilosin A, which exhibits observable but significantly decreased antibacterial activity compared to subtilosin A. These results provide valuable insights into the biosynthesis of subtilosin A and pave the way for future research on the sactipeptide family of natural products.