Lovato Martha A, Swairjo Manal A, Schimmel Paul
Skaggs Institute for Chemical Biology and the Departments of Molecular Biology and Chemistry, The Scripps Research Institute, BCC-379, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Mol Cell. 2004 Mar 26;13(6):843-51. doi: 10.1016/s1097-2765(04)00125-x.
The crystal structure of a catalytic fragment of Aquifex aeolicus AlaRS and additional data suggest how the critical G3:U70 identity element of its cognate tRNA acceptor stem is recognized. Though this identity element is conserved from bacteria to the cytoplasm of eukaryotes, Drosophila melanogaster mitochondrial (Dm mt) tRNA(Ala) contains a G:U base pair that has been translocated to the adjacent 2:71 position. This G2:U71 is the major determinant for identity of Dm mt tRNA(Ala). Sequence alignments showed that Dm mt AlaRS is differentiated from G3:U70-recognizing AlaRSs by an insertion of 27 amino acids in the region of the protein that contacts the acceptor stem. Precise deletion of this insertion from Dm mt AlaRS gave preferential recognition to a G3:U70-containing substrate. Larger or smaller deletions were ineffective. The crystal structure of the orthologous A. aeolicus protein places this insertion on the surface, where it can act as a hinge that provides positional switching of G:U recognition.
嗜热栖热菌丙氨酸-tRNA合成酶（AlaRS）催化片段的晶体结构及其他数据表明了其同源tRNA受体茎的关键G3:U70识别元件是如何被识别的。尽管该识别元件从细菌到真核生物细胞质都是保守的，但果蝇线粒体（Dm mt）tRNA（Ala）含有一个已易位至相邻2:71位置的G:U碱基对。这个G2:U71是Dm mt tRNA（Ala）识别的主要决定因素。序列比对显示，Dm mt AlaRS与识别G3:U70的AlaRS的区别在于，在该蛋白质与受体茎接触的区域插入了27个氨基酸。从Dm mt AlaRS中精确删除此插入片段后，它对含G3:U70的底物具有优先识别能力。更大或更小的删除都无效。同源嗜热栖热菌蛋白质的晶体结构将此插入片段置于表面，在那里它可以作为一个铰链，提供G:U识别的位置切换。
