Crystal structure of tRNA (m1G37) methyltransferase from Aquifex aeolicus at 2.6 Å resolution: A novel methyltransferase fold

Introduction. The Berkeley Structural Genomics Center (BSGC) has focused on Mycoplasma as its structural genomics target organisms because of their compact genome size as well as their relevance to human and animal pathogenicity (http://www.strgen.org). The gene for transfer RNA (m1G37) methyltransferase of Aquifex aeolicus (GI number 2983865) is one of the structural genomics targets of BSGC that has been selected as a homolog of the Mycoplasma pneumoniae (MP) gene MPN183, trmD (http:// www.strgen.org/status/mptargets.html). The protein structures coded by either gene are not known. It is one of the tRNA-modifying enzymes that catalyzes the transfer of methyl group from S-adenosyl-L-methionine (AdoMet) to guanosine at position 37, the nucleoside adjacent to and 3 of the anticodon. This protein is important for the maintenance of the correct reading frame during translation. In all organisms, the tRNA-reading codons CUN (Leu), CCN (Pro), and CGG (Arg) contain at position 37 1-methylguanosine (m1G37), and tRNA (m1G37) methyltransferases from members of all three phylogenetic domains show sequence similarities. Currently, no structural information is available for this protein family. Here, we report the crystal structure of the enzyme tRNA (m1G37) methyltransferase from Aquifex aeolicus at 2.6 Å resolution. The structure reveals a novel methyltransferase fold distinctly different from those of the most common methyltransferases.

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