Department of Life Sciences, National Central University, Zhongli District, Taoyuan 32001, Taiwan.
Department of Neurology, Taipei Veterans General Hospital, Beitou District, Taipei 11217, Taiwan.
Nucleic Acids Res. 2022 Feb 28;50(4):2190-2200. doi: 10.1093/nar/gkac026.
Unlike many other aminoacyl-tRNA synthetases, alanyl-tRNA synthetase (AlaRS) retains a conserved prototype structure throughout biology. While Caenorhabditis elegans cytoplasmic AlaRS (CeAlaRSc) retains the prototype structure, its mitochondrial counterpart (CeAlaRSm) contains only a residual C-terminal domain (C-Ala). We demonstrated herein that the C-Ala domain from CeAlaRSc robustly binds both tRNA and DNA. It bound different tRNAs but preferred tRNAAla. Deletion of this domain from CeAlaRSc sharply reduced its aminoacylation activity, while fusion of this domain to CeAlaRSm selectively and distinctly enhanced its aminoacylation activity toward the elbow-containing (or L-shaped) tRNAAla. Phylogenetic analysis showed that CeAlaRSm once possessed the C-Ala domain but later lost most of it during evolution, perhaps in response to the deletion of the T-arm (part of the elbow) from its cognate tRNA. This study underscores the evolutionary gain of C-Ala for docking AlaRS to the L-shaped tRNAAla.
与许多其他氨酰-tRNA 合成酶不同，丙氨酰-tRNA 合成酶（AlaRS）在整个生物学中保留了保守的原型结构。虽然秀丽隐杆线虫细胞质丙氨酰-tRNA 合成酶（CeAlaRSc）保留了原型结构，但它的线粒体同工酶（CeAlaRSm）仅含有残余的 C 末端结构域（C-Ala）。我们在此证明，CeAlaRSc 的 C-Ala 结构域能够与 tRNA 和 DNA 强烈结合。它结合了不同的 tRNA，但更喜欢 tRNAAla。从 CeAlaRSc 中删除该结构域会显著降低其氨酰化活性，而将该结构域融合到 CeAlaRSm 中会选择性地和明显地增强其对含肘（或 L 形）的 tRNAAla 的氨酰化活性。系统发育分析表明，CeAlaRSm 曾经拥有 C-Ala 结构域，但后来在进化过程中丢失了大部分结构域，这可能是对其同源 tRNA 的 T 臂（肘的一部分）缺失的一种反应。这项研究强调了 C-Ala 在将 AlaRS 对接至 L 形 tRNAAla 中的进化获得。
