title: A divalent metal ion-dependent N(1)-methyl transfer to G37-tRNA.
abstract: The catalytic mechanism of the majority of S-adenosyl methionine (AdoMet)-dependent methyl transferases requires no divalent metal ions. Here we report that methyl transfer from AdoMet to N(1) of G37-tRNA, catalyzed by the bacterial TrmD enzyme, is strongly dependent on divalent metal ions and that Mg(2+) is the most physiologically relevant. Kinetic isotope analysis, metal rescue, and spectroscopic measurements indicate that Mg(2+) is not involved in substrate binding, but in promoting methyl transfer. On the basis of the pH-activity profile indicating one proton transfer during the TrmD reaction, we propose a catalytic mechanism in which the role of Mg(2+) is to help to increase the nucleophilicity of N(1) of G37 and stabilize the negative developing charge on O(6) during attack on the methyl sulfonium of AdoMet. This work demonstrates how Mg(2+) contributes to the catalysis of AdoMet-dependent methyl transfer in one of the most crucial posttranscriptional modifications to tRNA.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10(th) Street, BLSB 220, Philadelphia, PA 19107, USA.
authors.forename: Reiko
authors.initials: R
authors.lastname: Sakaguchi
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10(th) Street, BLSB 220, Philadelphia, PA 19107, USA.
authors.forename: Georges
authors.initials: G
authors.lastname: Lahoud
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10(th) Street, BLSB 220, Philadelphia, PA 19107, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Christian
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10(th) Street, BLSB 220, Philadelphia, PA 19107, USA.
authors.forename: Howard
authors.initials: H
authors.lastname: Gamper
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10(th) Street, BLSB 220, Philadelphia, PA 19107, USA. Electronic address: ya-ming.hou@jefferson.edu.
authors.forename: Ya-Ming
authors.initials: YM
authors.lastname: Hou
mesh_terms: D055162:Biocatalysis; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism; D008670:Metals / Q000737:chemistry / Q000378:metabolism*; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism; D012359:tRNA Methyltransferases / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D007477:Ions; D008670:Metals; D012436:S-Adenosylmethionine; D012343:RNA, Transfer; C489297:TrmD protein, E coli; D012359:tRNA Methyltransferases; D008274:Magnesium