title: Determinants of the CmoB carboxymethyl transferase utilized for selective tRNA wobble modification.
abstract: Enzyme-mediated modifications at the wobble position of tRNAs are essential for the translation of the genetic code. We report the genetic, biochemical and structural characterization of CmoB, the enzyme that recognizes the unique metabolite carboxy-S-adenosine-L-methionine (Cx-SAM) and catalyzes a carboxymethyl transfer reaction resulting in formation of 5-oxyacetyluridine at the wobble position of tRNAs. CmoB is distinctive in that it is the only known member of the SAM-dependent methyltransferase (SDMT) superfamily that utilizes a naturally occurring SAM analog as the alkyl donor to fulfill a biologically meaningful function. Biochemical and genetic studies define the in vitro and in vivo selectivity for Cx-SAM as alkyl donor over the vastly more abundant SAM. Complementary high-resolution structures of the apo- and Cx-SAM bound CmoB reveal the determinants responsible for this remarkable discrimination. Together, these studies provide mechanistic insight into the enzymatic and non-enzymatic feature of this alkyl transfer reaction which affords the broadened specificity required for tRNAs to recognize multiple synonymous codons.
authors: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors: Jungwook
authors: J
authors: Kim
authors: Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors: Hui
authors: H
authors: Xiao
authors: Laboratory of Cell Biology and Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA.
authors: Junseock
authors: J
authors: Koh
authors: Chemical Biology Program, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
authors: Yikai
authors: Y
authors: Wang
authors: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors: Jeffrey B
authors: JB
authors: Bonanno
authors: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors: Keisha
authors: K
authors: Thomas
authors: Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, CA 94158, USA.
authors: Patricia C
authors: PC
authors: Babbitt
authors: Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, CA 94158, USA.
authors: Shoshana
authors: S
authors: Brown
authors: Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA.
authors: Young-Sam
authors: YS
authors: Lee
authors: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA Department of Physiology & Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461, USA steve.almo@einstein.yu.edu.
authors: Steven C
authors: SC
authors: Almo
mesh_terms: D001665:Binding Sites; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D008780:Methyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000031:analogs & derivatives* / Q000737:chemistry; D013816:Thermodynamics
chemical_list: C581857:4-(((5-(6-amino-9H-purin-9-yl)-3,4-dihydroxytetrahydrofuran-2-yl)methyl)(carboxylatomethyl)sulfonio)-2-ammoniobutanoate; D029968:Escherichia coli Proteins; D008024:Ligands; D012436:S-Adenosylmethionine; D012343:RNA, Transfer; C581859:CmoB protein, E coli; D008780:Methyltransferases