Determinants of the CmoB carboxymethyl transferase utilized for selective tRNA wobble modification.
Bottom Line: We report the genetic, biochemical and structural characterization of CmoB, the enzyme that recognizes the unique metabolite carboxy-S-adenosine-L-methionine (Cx-SAM) and catalyzes a carboxymethyl transfer reaction resulting in formation of 5-oxyacetyluridine at the wobble position of tRNAs.Biochemical and genetic studies define the in vitro and in vivo selectivity for Cx-SAM as alkyl donor over the vastly more abundant SAM.Together, these studies provide mechanistic insight into the enzymatic and non-enzymatic feature of this alkyl transfer reaction which affords the broadened specificity required for tRNAs to recognize multiple synonymous codons.
Affiliation: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.Show MeSH
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Mentions: Difference Fourier syntheses calculated after initial rounds of refinement, without the inclusion of ligand, exhibited features consistent with the binding of Cx-SAM in the catalytic site (Figure 3A). Continued refinement and modeling indicated that Cx-SAM is present at full occupancy and demonstrated similar atomic interactions in all 10 independent catalytic sites in both liganded structures.
Affiliation: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.