4jal
Crystal structure of tRNA (Um34/Cm34) methyltransferase TrmL from Escherichia coli with SAH
Structural highlights
FunctionTRML_ECOLI Methylates the ribose at the nucleotide 34 wobble position in the two leucyl isoacceptors tRNA(Leu)(CmAA) and tRNA(Leu)(cmnm5UmAA). Catalyzes the methyl transfer from S-adenosyl-L-methionine to the 2'-OH of the wobble nucleotide. Recognition of the target requires a pyridine at position 34 and N(6)-(isopentenyl)-2-methylthioadenosine at position 37.[1] Publication Abstract from PubMedUnlike other transfer RNAs (tRNA)-modifying enzymes from the SPOUT methyltransferase superfamily, the tRNA (Um34/Cm34) methyltransferase TrmL lacks the usual extension domain for tRNA binding and consists only of a SPOUT domain. Both the catalytic and tRNA recognition mechanisms of this enzyme remain elusive. By using tRNAs purified from an Escherichia coli strain with the TrmL gene deleted, we found that TrmL can independently catalyze the methyl transfer from S-adenosyl-L-methionine to and isoacceptors without the involvement of other tRNA-binding proteins. We have solved the crystal structures of TrmL in apo form and in complex with S-adenosyl-homocysteine and identified the cofactor binding site and a possible active site. Methyltransferase activity and tRNA-binding affinity of TrmL mutants were measured to identify residues important for tRNA binding of TrmL. Our results suggest that TrmL functions as a homodimer by using the conserved C-terminal half of the SPOUT domain for catalysis, whereas residues from the less-conserved N-terminal half of the other subunit participate in tRNA recognition. The tRNA recognition mechanism of the minimalist SPOUT methyltransferase, TrmL.,Liu RJ, Zhou M, Fang ZP, Wang M, Zhou XL, Wang ED Nucleic Acids Res. 2013 Jun 26. PMID:23804755[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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