Structural highlights
FunctionTRM1_PYRHO Dimethylates a single guanine residue at position 26 of a number of tRNAs using S-adenosyl-L-methionine as donor of the methyl groups (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedTrm1 catalyzes a two-step reaction, leading to mono- and dimethylation of guanosine at position 26 in most eukaryotic and archaeal tRNAs. We report the crystal structures of Trm1 from Pyrococcus horikoshii liganded with S-adenosyl-l-methionine or S-adenosyl-l-homocysteine. The protein comprises N-terminal and C-terminal domains with class I methyltransferase and novel folds, respectively. The methyl moiety of S-adenosyl-l-methionine points toward the invariant Phe27 and Phe140 within a narrow pocket, where the target G26 might flip in. Mutagenesis of Phe27 or Phe140 to alanine abolished the enzyme activity, indicating their role in methylating G26. Structural analyses revealed that the movements of Phe140 and the loop preceding Phe27 may be involved in dissociation of the monomethylated tRNA*Trm1 complex prior to the second methylation. Moreover, the catalytic residues Asp138, Pro139, and Phe140 are in a different motif from that in DNA 6-methyladenosine methyltransferases, suggesting a different methyl transfer mechanism in the Trm1 family. Crystal structure of tRNA N2,N2-guanosine dimethyltransferase Trm1 from Pyrococcus horikoshii.,Ihsanawati, Nishimoto M, Higashijima K, Shirouzu M, Grosjean H, Bessho Y, Yokoyama S J Mol Biol. 2008 Nov 21;383(4):871-84. Epub 2008 Sep 5. PMID:18789948[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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