Ahn Hyung Jun, Kim Hyeon-Woo, Yoon Hye-Jin, Lee Byung Il, Suh Se Won, Yang Jin Kuk
Structural Proteomics Laboratory, School of Chemistry and Molecular Engineering, Seoul National University, Seoul 151-742, Korea.
EMBO J. 2003 Jun 2;22(11):2593-603. doi: 10.1093/emboj/cdg269.
tRNA(m(1)G37)methyltransferase (TrmD) catalyzes the transfer of a methyl group from S-adenosyl-L- methionine (AdoMet) to G(37) within a subset of bacterial tRNA species, which have a G residue at the 36th position. The modified guanosine is adjacent to and 3' of the anticodon and is essential for the maintenance of the correct reading frame during translation. Here we report four crystal structures of TrmD from Haemophilus influenzae, as binary complexes with either AdoMet or S-adenosyl-L-homocysteine (AdoHcy), as a ternary complex with AdoHcy and phosphate, and as an apo form. This first structure of TrmD indicates that it functions as a dimer. It also suggests the binding mode of G(36)G(37) in the active site of TrmD and the catalytic mechanism. The N-terminal domain has a trefoil knot, in which AdoMet or AdoHcy is bound in a novel, bent conformation. The C-terminal domain shows structural similarity to trp repressor. We propose a plausible model for the TrmD(2)-tRNA(2) complex, which provides insights into recognition of the general tRNA structure by TrmD.
tRNA（m(1)G37）甲基转移酶（TrmD）催化将甲基从S - 腺苷 - L - 甲硫氨酸（AdoMet）转移至细菌tRNA种类的一个子集中第37位的鸟苷（G）上，这些tRNA在第36位有一个G残基。修饰后的鸟苷与反密码子相邻且在其3'端，对于翻译过程中维持正确的阅读框至关重要。在此我们报道了来自流感嗜血杆菌的TrmD的四个晶体结构，分别是与AdoMet或S - 腺苷 - L - 高半胱氨酸（AdoHcy）形成的二元复合物、与AdoHcy和磷酸盐形成的三元复合物以及无配体形式。TrmD的首个结构表明它以二聚体形式发挥作用。它还揭示了TrmD活性位点中G(36)G(37)的结合模式及催化机制。N端结构域有一个三叶结，其中AdoMet或AdoHcy以一种新颖的弯曲构象结合。C端结构域与色氨酸阻遏蛋白在结构上相似。我们提出了一个关于TrmD(2)-tRNA(2)复合物的合理模型，该模型为TrmD对一般tRNA结构的识别提供了见解。
