Waye M M, Winter G, Wilkinson A J, Fersht A R
EMBO J. 1983;2(10):1827-9. doi: 10.1002/j.1460-2075.1983.tb01665.x.
The X-ray crystallographic structure of tyrosyl-tRNA synthetase (TyrTS) comprises only the N-terminal 320 amino acids of the molecule as the C-terminal 99 amino acids are poorly ordered in the crystal. A new technique, employing a single-stranded M13 splint, has been used to direct a deletion in the cloned gene of TyrTS so as to remove the disordered C-terminal region. We find that the truncated enzyme catalyses the formation of tyrosyl adenylate with unchanged Kcat and Km values and the crystallographic model must therefore include all the binding and catalytic residues involved in tyrosine activation. However, the truncated enzyme no longer binds tRNATyr or transfers tyrosine to tRNATyr. This indicates that the structural division of TyrTS is equally a functional one: the N-terminal structural domain catalyses tyrosine activation while the disordered C-terminal domain carries major determinants in tRNA binding.
酪氨酰 - tRNA合成酶（TyrTS）的X射线晶体结构仅包含该分子N端的320个氨基酸，因为C端的99个氨基酸在晶体中排列无序。一种采用单链M13夹板的新技术已被用于指导TyrTS克隆基因中的缺失，以去除无序的C端区域。我们发现，截短的酶催化酪氨酰腺苷酸的形成，其催化常数（Kcat）和米氏常数（Km）值不变，因此晶体学模型必须包括参与酪氨酸活化的所有结合和催化残基。然而，截短的酶不再结合tRNATyr，也不再将酪氨酸转移到tRNATyr上。这表明TyrTS的结构划分同样也是功能划分：N端结构域催化酪氨酸活化，而无序的C端结构域携带tRNA结合的主要决定因素。
