Mycobacterium tuberculosis Rv2118c codes for single-component homotetrameric $m^1A58$ tRNA methyltransferase

Varshney, U and Ramesh, V and Madabushi, A and Gaur, R and Subramanya, HS and RajBhandary, UL (2004) Mycobacterium tuberculosis Rv2118c codes for single-component homotetrameric $m^1A58$ tRNA methyltransferase. In: Nucleic Acids Research, 32 (3). pp. 1018-1027.

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Abstract

ModiÆed nucleosides in tRNAs play important roles in tRNA structure, biosynthesis and function, and serve as crucial determinants of bacterial growth and virulence. In the yeast Saccharomyces cerevisiae, mutants defective in $N^1-$methylation of a highly conserved adenosine (A58) in the TYC loop of initiator tRNA are non-viable. The yeast $m^1A58$ methyltransferase is a heterotetramer consisting of two different polypeptide chains, Gcd14p and Gcd10p. Interestingly, while m1A58 is not found in most eubacteria, the mycobacterial tRNAs have m1A58. Here, we report on the cloning, overexpression, puriÆcation and biochemical characterization of the Rv2118c gene-encoded protein (Rv2118p) from Mycobacterium tuberculosis, which is homologous to yeast Gcd14p. We show that Rv2118c codes for a protein of ~31 kDa. Activity assays, modiÆed base analysis and primer extension experiments using reverse transcriptase reveal that Rv2118p is an S-adenosyl-L-methionine-dependent methyltransferase which carries out $m^1A58$ modiÆcation in tRNAs, both in vivo and in vitro. Remarkably, when expressed in Escherichia coli, the enzyme methylates the endogenous E.coli initiator tRNA essentially quantitatively. Furthermore, unlike its eukaryotic counterpart, which is a heterotetramer, the mycobacterial enzyme is a homotetramer. Also, the presence of rT modiÆcation at position 54, which was found to inhibit the Tetrahymena pyriformis enzyme, does not affect the activity of Rv2118p. Thus, the mycobacterial $m^1A58$ tRNA methyltransferase possesses distinct biochemical properties. We discuss aspects of the biological relevance of Rv2118p in M.tuberculosis, and its potential use as a drug target to control the growth of mycobacteria.

Item Type:	Journal Article
Publication:	Nucleic Acids Research
Publisher:	Oxford University Press
Additional Information:	The copyright belongs to Oxford University Press.
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited:	27 May 2006
Last Modified:	19 Sep 2010 04:27
URI:	http://eprints.iisc.ac.in/id/eprint/6886

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