Structure and tRNA Specificity of MibB, a Lantibiotic Dehydratase from Actinobacteria Involved in NAI-107 Biosynthesis

摘要

Class I lantibiotic dehydratases dehydrate selected Ser/Thr residues of a precursor peptide. Recent studies demonstrated the requirement of glutamyltRNA Glu for Ser/Thr activation by one of these enzymes (NisB) from the Firmicute Lactococcus lactis. However, the generality of glutamyl-tRNAGlu usage and the tRNA specificity of lantibiotic dehydratases have not been established. Here we report the 2.7-?resolution crystal structure, along with the glutamyl-tRNAGlu utilization of MibB, a lantibiotic dehydratase from the Actinobacterium Microbispora sp. 107891 involved in the biosynthesis of the clinical candidate NAI-107. Biochemical assays revealed nucleotides A73 and U72 within the tRNAGlu acceptor stem to be important for MibB glutamyltRNA Glu usage. Using this knowledge, an expression system for the production of NAI-107 analogs in Escherichia coli was developed, overcoming the inability of MibB to utilize E. coli tRNAGlu. Our work provides evidence for a common tRNAGlu-dependent dehydration mechanism, paving the way for the characterization of lantibiotics from various phyla.