title: Biosynthesis of Branched Alkoxy Groups: Iterative Methyl Group Alkylation by a Cobalamin-Dependent Radical SAM Enzyme.
abstract: The biosynthesis of branched alkoxy groups, such as the unique t-butyl group found in a variety of natural products, is still poorly understood. Recently, cystobactamids were isolated and identified from Cystobacter sp as novel antibacterials. These metabolites contain an isopropyl group proposed to be formed using CysS, a cobalamin-dependent radical S-adenosylmethionine (SAM) methyltransferase. Here, we reconstitute the CysS-catalyzed reaction, on p-aminobenzoate thioester substrates, and demonstrate that it not only catalyzes sequential methylations of a methyl group to form ethyl and isopropyl groups but remarkably also sec-butyl and t-butyl groups. To our knowledge, this is the first in vitro reconstitution of a cobalamin-dependent radical SAM enzyme catalyzing the conversion of a methyl group to a t-butyl group.
authors.affiliation: Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Yuanyou
authors.identifier: 0000-0002-9774-7877
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University , Universitätscampus E8.1, D-66123 Saarbrücken, Germany.
authors.forename: Bastien
authors.initials: B
authors.lastname: Schnell
authors.affiliation: Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University , Universitätscampus E8.1, D-66123 Saarbrücken, Germany.
authors.forename: Sascha
authors.initials: S
authors.lastname: Baumann
authors.affiliation: Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University , Universitätscampus E8.1, D-66123 Saarbrücken, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Müller
authors.affiliation: Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Tadhg P
authors.initials: TP
authors.lastname: Begley
mesh_terms: D000478:Alkylation; D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000737:chemistry; D001216:Asparagine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D055162:Biocatalysis; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism; D008738:Methyl Ethers / Q000737:chemistry / Q000378:metabolism*; D008780:Methyltransferases / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D009574:Nitro Compounds / Q000737:chemistry; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism*; D014805:Vitamin B 12 / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D005609:Free Radicals; D008738:Methyl Ethers; D009574:Nitro Compounds; C000600617:cystobactamid 919-2; D001216:Asparagine; D012436:S-Adenosylmethionine; D008780:Methyltransferases; D014805:Vitamin B 12