分子结构的S124A、S124T S124V基因定点突变体的UDP-galactose 4-epimerase从大肠杆菌。
文章的细节
-
引用
复制到剪贴板 -
Thoden JB,霍顿Gulick点,嗯
分子结构的S124A、S124T S124V基因定点突变体的UDP-galactose 4-epimerase从大肠杆菌。
生物化学。1997年9月2,36 (35):10685 - 95。
- PubMed ID
-
9271499 (在PubMed]
- 文摘
-
UDP-galactose 4-epimerase糖代谢中起着至关重要的作用,催化UDP-galactose和UDP-glucose的互变现象。最初,它是假定酶含有一个“传统”催化基础服务抽象一个质子从4羟基群UDP-glucose或UDP-galactose基板过程中反应。然而,最近的高分辨率x射线晶体对大肠杆菌的蛋白质的分析证明了缺乏一个天冬氨酸,谷氨酸或面向正确组氨酸残基的活性部位内裂等服务功能的作用。相反,x射线晶体epimerase.NADH的调查。UDP-glucose流产复杂从这个实验室已经表明,爵士124年和149年酪氨酸都位于氢键距离4 ',3 '羟基组的糖,分别。124年测试的结构作用Ser差向异构酶的反应机理,三个基因定点突变的蛋白质,即S124A, S124T,和S124V S124A.NADH的构造和水晶。UDP, S124A.NADH。UDP-glucose S124T。NADH。UDP-glucose, S124V.NADH。UDP-glucose复合物被种植。 All of the crystals employed in this investigation belonged to the space group P3221 with the following unit cell dimensions: a = b = 83.8 A, c = 108.4 A, and one subunit per asymmetric unit. X-ray data sets were collected to at least 2.15 A resolution, and each protein model was subsequently refined to an R value of lower than 19.0% for all measured X-ray data. The investigations described here demonstrate that the decreases in enzymatic activities observed for these mutant proteins are due to the loss of a properly positioned hydroxyl group at position 124 and not to major tertiary and quaternary structural perturbations. In addition, these structures demonstrate the importance of a hydroxyl group at position 124 in stabilizing the anti conformation of the nicotinamide ring as observed in the previous structural analysis of the epimerase.NADH. UDP complex.