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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of tRNA N2,N2-guanosine dimethyltransferase Trm1 from Pyrococcus horikoshii.
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Crystal structure of tRNA N2,N2-guanosine dimethyltransferase Trm1 from Pyrococcus horikoshii.

机译：贺氏热球菌的tRNA N2，N2-鸟苷二甲基转移酶Trm1的晶体结构。

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摘要

Trm1 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.
机译：Trm1催化两步反应，导致大多数真核生物和古细菌tRNA中第26位的鸟苷单和二甲基化。我们报告了由S-腺苷-1-蛋氨酸或S-腺苷-1-高半胱氨酸配体的火球菌Trm1的晶体结构。该蛋白质包含分别具有I类甲基转移酶和新折叠的N末端和C末端结构域。 S-腺苷-1-甲硫氨酸的甲基部分指向狭窄口袋中的​​不变Phe27和Phe140，目标G26可能在其中插入。Phe27或Phe140突变为丙氨酸的突变消除了酶活性，表明它们在甲基化G26中的作用。结构分析表明，在第二次甲基化之前，Phe140和Phe27之前的环的运动可能与单甲基化的tRNA * Trm1复合体的解离有关。此外，催化残基Asp138，Pro139和Phe140与DNA 6-甲基腺苷甲基转移酶具有不同的基序，表明Trm1家族中的甲基转移机制不同。

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