Yang Xiang-Lei, Kapoor Mili, Otero Francella J, Slike Bonnie M, Tsuruta Hiro, Frausto Ricardo, Bates Alison, Ewalt Karla L, Cheresh David A, Schimmel Paul
Department of Molecular Biology and Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Chem Biol. 2007 Dec;14(12):1323-33. doi: 10.1016/j.chembiol.2007.10.016.
Disease-causing mutations occur in genes for aminoacyl tRNA synthetases. That some mutations are dominant suggests a gain of function. Native tRNA synthetases, such as tyrosyl-tRNA synthetase (TyrRS) and tryptophanyl-tRNA synthetase, catalyze aminoacylation and are also procytokines that are activated by natural fragmentation. In principle, however, gain-of-function phenotypes could arise from mutational activation of synthetase procytokines. From crystal structure analysis, we hypothesized that a steric block of a critical Glu-Leu-Arg (ELR) motif in full-length TyrRS suppresses the cytokine activity of a natural fragment. To test this hypothesis, we attempted to uncover ELR in the procytokine by mutating a conserved tyrosine (Y341) that tethers ELR. Site-specific proteolytic cleavage and small-angle X-ray scattering established subtle opening of the structure by the mutation. Strikingly, four different assays demonstrated mutational activation of cytokine functions. The results prove the possibilities for constitutive gain-of-function mutations in tRNA synthetases.
致病突变发生在氨酰tRNA合成酶的基因中。一些突变是显性的，这表明存在功能获得。天然的tRNA合成酶，如酪氨酰-tRNA合成酶（TyrRS）和色氨酰-tRNA合成酶，催化氨酰化反应，同时也是通过自然裂解而被激活的前细胞因子。然而，从理论上讲，功能获得性表型可能源于合成酶前细胞因子的突变激活。通过晶体结构分析，我们推测全长TyrRS中关键的Glu-Leu-Arg（ELR）基序的空间位阻抑制了天然片段的细胞因子活性。为了验证这一假设，我们试图通过突变连接ELR的保守酪氨酸（Y341）来揭示前细胞因子中的ELR。位点特异性蛋白水解切割和小角X射线散射表明，该突变使结构发生了微妙的开放。引人注目的是，四种不同的检测方法都证明了细胞因子功能的突变激活。这些结果证明了tRNA合成酶中存在组成型功能获得性突变的可能性。
