A radically different mechanism for S-adenosylmethionine-dependent methyltransferases

Tyler L. Grove, Jack S. Benner, Matthew I. Radle, Jessica H. Ahlum, Bradley J. Landgraf, Carsten Krebs, Squire J. Booker

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Abstract

Methylation of small molecules and macromolecules is crucial in metabolism, cell signaling, and epigenetic programming and is most often achieved by S-adenosylmethionine (SAM) - dependent methyltransferases. Most employ an S N2 mechanism to methylate nucleophilic sites on their substrates, but recently, radical SAM enzymes have been identified that methylate carbon atoms that are not inherently nucleophilic via the intermediacy of a 5′-deoxyadenosyl 5′-radical. We have determined the mechanisms of two such reactions targeting the sp2-hybridized carbons at positions 2 and 8 of adenosine 2503 in 23S ribosomal RNA, catalyzed by RlmN and Cfr, respectively. In neither case is a methyl group transferred directly from SAM to the RNA; rather, both reactions proceed by a ping-pong mechanism involving intermediate methylation of a conserved cysteine residue.

Original languageEnglish (US)
Pages (from-to)604-607
Number of pages4
JournalScience
Volume332
Issue number6029
DOIs
StatePublished - Apr 29 2011

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All Science Journal Classification (ASJC) codes

  • General

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