Perona J J, Rould M A, Steitz T A, Risler J L, Zelwer C, Brunie S
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
Proc Natl Acad Sci U S A. 1991 Apr 1;88(7):2903-7. doi: 10.1073/pnas.88.7.2903.
Detailed comparisons between the structures of the tRNA-bound Escherichia coli glutaminyl-tRNA (Gln-tRNA) synthetase [L-glutamine:tRNA(Gln) ligase (AMP-forming), EC 6.1.1.18] and recently refined E. coli methionyl-tRNA (Met-tRNA) synthetase [L-methionine:tRNA(Met) ligase (AMP-forming), EC 6.1.1.10] reveal significant similarities beyond the anticipated correspondence of their respective dinucleotide-fold domains. One similarity comprises a 23-amino acid alpha-helix-turn-beta-strand motif found in each enzyme within a domain that is inserted between the two halves of the dinucleotide binding fold. A second correspondence, which consists of two alpha-helices connected by a large loop and beta-strand, is located in the Gln-tRNA synthetase within a region that binds the inside corner of the "L"-shaped tRNA molecule. This structural motif contains a long alpha-helix, which extends along the entire length of the D and anticodon stems of the complexed tRNA. We suggest that the positioning of this helix relative to the dinucleotide fold plays a critical role in ensuring the proper global orientation of tRNA(Gln) on the surface of the enzyme. The structural correspondences suggest a similar overall orientation of binding of tRNA(Met) and tRNA(Gln) to their respective synthetases.
对结合了tRNA的大肠杆菌谷氨酰胺-tRNA合成酶[L-谷氨酰胺：tRNA（Gln）连接酶（形成AMP），EC 6.1.1.18]与最近优化的大肠杆菌甲硫氨酸-tRNA合成酶[L-甲硫氨酸：tRNA（Met）连接酶（形成AMP），EC 6.1.1.10]的结构进行的详细比较揭示了显著的相似性，这些相似性超出了它们各自二核苷酸折叠结构域预期的对应关系。其中一个相似之处是在每个酶中位于二核苷酸结合折叠两半之间插入的结构域内发现的一个由23个氨基酸组成的α-螺旋-转角-β-链基序。第二个对应之处由两个通过大的环和β-链连接的α-螺旋组成，位于谷氨酰胺-tRNA合成酶中与“L”形tRNA分子内角结合的区域内。这个结构基序包含一个长的α-螺旋，它沿着复合tRNA的D茎和反密码子茎的整个长度延伸。我们认为，该螺旋相对于二核苷酸折叠的定位在确保tRNA（Gln）在酶表面的正确整体取向中起着关键作用。这些结构对应关系表明tRNA（Met）和tRNA（Gln）与其各自合成酶的结合具有相似的整体取向。
