Title: Identification and Characterization of the Sulfazecin Monobactam Biosynthetic Gene Cluster Li R, Oliver RA, Townsend CA Ref: Cell Chemical Biology, 24:24, 2017 : PubMed
The monobactams, exemplified by the natural product sulfazecin, are the only class of beta-lactam antibiotics not inactivated by metallo-beta-lactamases, which confer bacteria with extended-spectrum beta-lactam resistance. We screened a transposon mutagenesis library from Pseudomonas acidophila ATCC 31363 and isolated a sulfazecin-deficient mutant that revealed a gene cluster encoding two non-ribosomal peptide synthetases (NRPSs), a methyltransferase, a sulfotransferase, and a dioxygenase. Three modules and an aberrant C-terminal thioesterase (TE) domain are distributed across the two NRPSs. Biochemical examination of the adenylation (A) domains provided evidence that L-2,3-diaminopropionate, not L-serine as previously thought, is the direct source of the beta-lactam ring of sulfazecin. ATP/PPi exchange assay also revealed an unusual substrate selectivity shift of one A domain when expressed with or without the immediately upstream condensation domain. Gene inactivation analysis defined a cluster of 13 open reading frames sufficient for sulfazecin production, precursor synthesis, self-resistance, and regulation. The identification of a key intermediate supported a proposed NRPS-mediated mechanism of sulfazecin biosynthesis and beta-lactam ring formation distinct from the nocardicins, another NRPS-derived subclass of monocyclic beta-lactam. These findings will serve as the basis for further biosynthetic research and potential engineering of these important antibiotics.
Li R, Oliver RA, Townsend CA (2017) Identification and Characterization of the Sulfazecin Monobactam Biosynthetic Gene Cluster Cell Chemical Biology24: 24-34
Li R, Oliver RA, Townsend CA (2017) Cell Chemical Biology24: 24-34