title: A B12-dependent radical SAM enzyme involved in oxetanocin A biosynthesis.
abstract: Oxetanocin A (OXT-A) is a potent antitumour, antiviral and antibacterial compound. Biosynthesis of OXT-A has been linked to a plasmid-borne Bacillus megaterium gene cluster that contains four genes: oxsA, oxsB, oxrA and oxrB. Here we show that both the oxsA and oxsB genes are required for the production of OXT-A. Biochemical analysis of the encoded proteins, a cobalamin (Cbl)-dependent S-adenosylmethionine (AdoMet) radical enzyme, OxsB, and an HD-domain phosphohydrolase, OxsA, reveals that OXT-A is derived from a 2'-deoxyadenosine phosphate in an OxsB-catalysed ring contraction reaction initiated by hydrogen atom abstraction from C2'. Hence, OxsB represents the first biochemically characterized non-methylating Cbl-dependent AdoMet radical enzyme. X-ray analysis of OxsB reveals the fold of a Cbl-dependent AdoMet radical enzyme, a family of enzymes with an estimated 7,000 members. Overall, this work provides a framework for understanding the interplay of AdoMet and Cbl cofactors and expands the catalytic repertoire of Cbl-dependent AdoMet radical enzymes.
authors.affiliation: Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bridwell-Rabb
authors.affiliation: Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, Texas 78712, USA.|Department of Chemistry, University of Texas, Austin, Texas 78712, USA.
authors.forename: Aoshu
authors.initials: A
authors.lastname: Zhong
authors.affiliation: Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, Texas 78712, USA.|Department of Chemistry, University of Texas, Austin, Texas 78712, USA.
authors.forename: He G
authors.initials: HG
authors.lastname: Sun
authors.affiliation: Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Drennan
authors.affiliation: Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, Texas 78712, USA.|Department of Chemistry, University of Texas, Austin, Texas 78712, USA.
authors.forename: Hung-Wen
authors.initials: HW
authors.lastname: Liu
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D000249:Adenosine Monophosphate / Q000378:metabolism; D001410:Bacillus megaterium / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D003067:Coenzymes / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003838:Deoxyadenine Nucleotides / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics; D008958:Models, Molecular; D005810:Multigene Family / Q000235:genetics; D011487:Protein Conformation; D012436:S-Adenosylmethionine / Q000378:metabolism*; D014805:Vitamin B 12 / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003067:Coenzymes; D003838:Deoxyadenine Nucleotides; C051061:oxetanocin; D000249:Adenosine Monophosphate; D012436:S-Adenosylmethionine; D000225:Adenine; D014805:Vitamin B 12