Truong Lena, Hevener Kirk E, Rice Amy J, Patel Kavankumar, Johnson Michael E, Lee Hyun
Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland Ave., Suite 3100, Chicago, IL 60607-7173, USA.
Protein Expr Purif. 2013 Mar;88(1):98-106. doi: 10.1016/j.pep.2012.11.018. Epub 2012 Dec 13.
Staphylococcus aureus is a pathogenic bacterium that causes a variety of mild to lethal human diseases. The rapid spread of multidrug-resistant strains makes the discovery of new antimicrobial agents critical. Dihydroorotase (PyrC), the third enzyme in the bacterial pyrimidine biosynthesis pathway, is structurally and mechanistically distinct from its mammalian counterpart. It has been confirmed to be essential in S. aureus making it an attractive antibacterial drug target. No protocol to express and purify S. aureus PyrC (SaPyrC) has been reported. To obtain the SaPyrC enzyme and overcome anticipated solubility problems, the SaPyrC gene was cloned into the pET-SUMO vector. The N-terminal His-SUMO fused SaPyrC was expressed in Escherichia coli BL21 (DE3) with an HRV 3C protease recognition site inserted between the SUMO tag and SaPyrC to allow for improved cleavage by HRV protease. Purification of cleaved protein using HisTrap affinity and gel filtration columns resulted in native SaPyrC with estimated 95% purity and 40% yield. Both His-SUMO tagged and native SaPyrC form dimers, and enzyme characterization studies have shown that the His-SUMO tag affects enzyme activity slightly. Forward and reverse kinetic rate constants for both tagged and native SaPyrC were determined, and pH profiling studies revealed the optimal pH values for forward and reverse reactions.
金黄色葡萄球菌是一种致病性细菌,可导致多种从轻度到致命的人类疾病。多重耐药菌株的迅速传播使得发现新的抗菌剂至关重要。二氢乳清酸酶(PyrC)是细菌嘧啶生物合成途径中的第三种酶,其结构和作用机制与哺乳动物的对应物不同。已证实它在金黄色葡萄球菌中是必需的,这使其成为有吸引力的抗菌药物靶点。尚未有报道表达和纯化金黄色葡萄球菌PyrC(SaPyrC)的方案。为了获得SaPyrC酶并克服预期的溶解性问题,将SaPyrC基因克隆到pET-SUMO载体中。N端His-SUMO融合的SaPyrC在大肠杆菌BL21(DE3)中表达,在SUMO标签和SaPyrC之间插入了一个HRV 3C蛋白酶识别位点,以便HRV蛋白酶更好地切割。使用HisTrap亲和柱和凝胶过滤柱纯化切割后的蛋白,得到了纯度估计为95%、产率为40%的天然SaPyrC。His-SUMO标签化的和天然的SaPyrC均形成二聚体,酶学特性研究表明His-SUMO标签对酶活性有轻微影响。测定了标签化和天然SaPyrC的正向和反向动力学速率常数,pH谱研究揭示了正向和反向反应的最佳pH值。