守恒的赖氨酸残基的位置和功能角色鼠伤寒沙门氏菌orotate phosphoribosyltransferase。
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多尔夫曼RH Ozturk DH, Scapin G, Sacchettini JC, Grubmeyer C
守恒的赖氨酸残基的位置和功能角色鼠伤寒沙门氏菌orotate phosphoribosyltransferase。
生物化学。1995年8月29日,34 (34):10755 - 63。
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7545005 (在PubMed]
- 文摘
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鼠伤寒沙门氏菌orotate phosphoribosyltransferase (OPRTase)催化的形成orotidine 5 '一磷酸(OMP)从orotate alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP)。有五个高度保守的赖氨酸残基(Lys-19、-26、-73、-100和-103年)在美国沙门氏菌感染OPRTase。在这里,我们报告的结果诱变和衬底模拟研究调查的功能角色这些赖氨酸。结合信息从x射线晶体学[Scapin, G。Grubmeyer C。& Sacchettini j . c(1994)生物化学33岁,1287 - 1294;Scapin G。Ozturk, d . H。Grubmeyer C。& Sacchettini j . C(1995)生物化学34岁,10744 - 10754],序列比较,和化学改性(Grubmeyer C。普- E。与多尔夫曼,r(1993)生物。化学。268年,20299 - 20304],这工作许可证的分配函数的五个守恒的赖氨酸。 Lys-19 is external to the active site, and its mutation to glutamine had little effect on enzyme activity. Lys-26 forms a hydrogen bond to OMP at the 3'-hydroxyl group, and its mutation produced 3-10-fold decreases in kcat. Lys-73 extends into the active site, and a conformational change allows it to interact with either the 5'-phosphate of OMP or the 2-hydroxyl and alpha-phosphoryl oxygen of PRPP in their respective substrate complexes. Mutation of Lys-73 produced a 50-100-fold decrease in kcat and an 8-12-fold increase in the KM value for PRPP. Mutation of Lys-100 produced a 5-fold decrease in kcat and a 3-fold increase in the KM for PRPP, consistent with its location within the active site, near the pyrophosphate moiety of PRPP.(ABSTRACT TRUNCATED AT 250 WORDS)