Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea.
Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Korea.
Mol Cells. 2020 Apr 30;43(4):350-359. doi: 10.14348/molcells.2020.2287.
Pathogenic aminoacyl-tRNA synthetases (ARSs) are attractive targets for anti-infective agents because their catalytic active sites are different from those of human ARSs. Mupirocin is a topical antibiotic that specifically inhibits bacterial isoleucy-ltRNA synthetase (IleRS), resulting in a block to protein synthesis. Previous studies on IleRS indicated that mupirocin-resistance of eukaryotic IleRS is primarily due to differences in two amino acids, His581 and Leu583, in the active site. However, without a eukaryotic IleRS structure, the structural basis for mupirocin-resistance of eukaryotic IleRS remains elusive. Herein, we determined the crystal structure of IleRS complexed with Ile-AMP at 2.9 Å resolution. The largest difference between eukaryotic and prokaryotic IleRS enzymes is closure of the active site pocket by Phe55 in the HIGH loop; Arg410 in the CP core loop; and the second Lys in the KMSKR loop. The Ile-AMP product is lodged in a closed active site, which may restrict its release and thereby enhance catalytic efficiency. The compact active site also prevents the optimal positioning of the 9-hydroxynonanoic acid of mupirocin and plays a critical role in resistance of eukaryotic IleRS to anti-infective agents.
致病氨酰-tRNA 合成酶（ARSs）是抗传染药物的有吸引力的靶标，因为它们的催化活性部位与人类 ARSs 不同。莫匹罗星是一种局部抗生素，特异性抑制细菌异亮氨酰-tRNA 合成酶（IleRS），导致蛋白质合成受阻。先前对 IleRS 的研究表明，真核 IleRS 的耐莫匹罗星性主要归因于活性部位的两个氨基酸，组氨酸 581 和亮氨酸 583 的差异。然而，由于没有真核 IleRS 的结构，真核 IleRS 耐莫匹罗星的结构基础仍然难以捉摸。在此，我们以 2.9 Å 的分辨率确定了 IleRS 与 Ile-AMP 复合物的晶体结构。真核和原核 IleRS 酶之间最大的区别是 HIGH 环中的苯丙氨酸 55、CP 核心环中的精氨酸 410 和 KMSKR 环中的第二个赖氨酸封闭了活性部位口袋。Ile-AMP 产物位于封闭的活性部位，这可能限制其释放并从而增强催化效率。紧凑的活性部位还阻止了莫匹罗星的 9-羟基壬酸的最佳定位，并在真核 IleRS 对抗感染药物的抗性中发挥关键作用。
