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Title: Structural Basis for Methyl Transfer by a Radical SAM Enzyme

The radical S-adenosyl-l-methionine (SAM) enzymes RlmN and Cfr methylate 23S ribosomal RNA, modifying the C2 or C8 position of adenosine 2503. The methyl groups are installed by a two-step sequence involving initial methylation of a conserved Cys residue (RlmN Cys{sup 355}) by SAM. Methyl transfer to the substrate requires reductive cleavage of a second equivalent of SAM. Crystal structures of RlmN and RlmN with SAM show that a single molecule of SAM coordinates the [4Fe-4S] cluster. Residue Cys{sup 355} is S-methylated and located proximal to the SAM methyl group, suggesting the SAM that is involved in the initial methyl transfer binds at the same site. Thus, RlmN accomplishes its complex reaction with structural economy, harnessing the two most important reactivities of SAM within a single site.
Authors:
; ; ; ; ;  [1] ;  [2]
  1. (NWU)
  2. (
Publication Date:
OSTI Identifier:
1020581
Resource Type:
Journal Article
Resource Relation:
Journal Name: Science; Journal Volume: 332; Journal Issue: 05, 2011
Research Org:
Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
Sponsoring Org:
NIH
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ADENOSINE; CLEAVAGE; CRYSTAL STRUCTURE; ENZYMES; METHYLATION; RADICALS; RESIDUES; RIBOSOMAL RNA; SUBSTRATES