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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.

SUBMITTER: Sakaguchi R

PROVIDER: S-EPMC4224600 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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A divalent metal ion-dependent N(1)-methyl transfer to G37-tRNA.

Sakaguchi Reiko R Lahoud Georges G Christian Thomas T Gamper Howard H Hou Ya-Ming YM

Chemistry & biology 20140911 10

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 t ...[more]

PMID: 25219964

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