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Chem Biol. 2014 Oct 23;21(10):1351-1360. doi: 10.1016/j.chembiol.2014.07.023. Epub 2014 Sep 11.

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

Author information

1
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10(th) Street, BLSB 220, Philadelphia, PA 19107, USA.
2
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.

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.

PMID:
25219964
PMCID:
PMC4224600
DOI:
10.1016/j.chembiol.2014.07.023
[Indexed for MEDLINE]
Free PMC Article

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