Wang Z, Choudhary A, Ledvina P S, Quiocho F A
Structural and Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, Texas 77030.
J Biol Chem. 1994 Oct 7;269(40):25091-4. doi: 10.2210/pdb1pbp/pdb.
Phosphorous, primarily in the form of phosphate, is a critical nutrient for the life of a cell. We have previously determined the 1.7-A resolution structure of the phosphate-binding protein, an initial receptor for the high-affinity phosphate active transport system or permease in Escherichia coli (Luecke, H., and Quiocho, F.A. (1990) Nature 347, 402-406). This structure is the first to reveal the key role of hydrogen bonding interactions in conferring the high specificity of the permease, a specificity also shared by other phosphate transport systems. Both monobasic and dibasic phosphates are recognized by the phosphate-binding protein with Asp56 playing a key role. Here we report site-directed mutagenesis, ligand binding, and crystallographic studies of the binding protein which show that introduction of one additional Asp by mutagenesis of the Thr141 in the ligand-binding site restricts binding to only the monobasic phosphate.
磷主要以磷酸盐的形式存在，是细胞生命活动所必需的关键营养素。我们之前已经确定了磷酸盐结合蛋白的1.7埃分辨率结构，它是大肠杆菌中高亲和力磷酸盐主动运输系统或通透酶的初始受体（Luecke, H., and Quiocho, F.A. (1990) Nature 347, 402 - 406）。该结构首次揭示了氢键相互作用在赋予通透酶高特异性方面的关键作用，这种特异性也为其他磷酸盐运输系统所共有。一价磷酸盐和二价磷酸盐都能被磷酸盐结合蛋白识别，其中天冬氨酸56发挥着关键作用。在此，我们报告了对该结合蛋白的定点诱变、配体结合及晶体学研究，这些研究表明，通过对配体结合位点的苏氨酸141进行诱变引入一个额外的天冬氨酸，会使结合仅限于一价磷酸盐。
