Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
J Biol Chem. 2009 Nov 27;284(48):33169-76. doi: 10.1074/jbc.M109.057612. Epub 2009 Sep 28.
The bacterial phosphoenolpyruvate (PEP) sugar phosphotransferase system mediates sugar uptake and controls the carbon metabolism in response to carbohydrate availability. Enzyme I (EI), the first component of the phosphotransferase system, consists of an N-terminal protein binding domain (EIN) and a C-terminal PEP binding domain (EIC). EI transfers phosphate from PEP by double displacement via a histidine residue on EIN to the general phosphoryl carrier protein HPr. Here we report the 2.4 A crystal structure of the homodimeric EI from Staphylococcus aureus. EIN consists of the helical hairpin HPr binding subdomain and the phosphorylatable betaalpha phospho-histidine (P-His) domain. EIC folds into an (betaalpha)(8) barrel. The dimer interface of EIC buries 1833 A(2) of accessible surface per monomer and contains two Ca(2+) binding sites per dimer. The structures of the S. aureus and Escherichia coli EI domains (Teplyakov, A., Lim, K., Zhu, P. P., Kapadia, G., Chen, C. C., Schwartz, J., Howard, A., Reddy, P. T., Peterkofsky, A., and Herzberg, O. (2006) Proc. Natl. Acad. Sci. U.S.A. 103, 16218-16223) are very similar. The orientation of the domains relative to each other, however, is different. In the present structure the P-His domain is docked to the HPr binding domain in an orientation appropriate for in-line transfer of the phosphate to the active site histidine of the acceptor HPr. In the E. coli structure the phospho-His of the P-His domain projects into the PEP binding site of EIC. In the S. aureus structure the crystallographic temperature factors are lower for the HPr binding domain in contact with the P-His domain and higher for EIC. In the E. coli structure it is the reverse.
细菌磷酸烯醇式丙酮酸（PEP）磷酸转移酶系统介导糖摄取，并根据碳水化合物的可用性控制碳代谢。磷酸转移酶系统的第一个组成部分酶 I（EI）由 N 端蛋白结合结构域（EIN）和 C 端 PEP 结合结构域（EIC）组成。EI 通过 EIN 上的组氨酸残基将磷酸从 PEP 中通过双置换转移到通用磷酸载体蛋白 HPr。在这里，我们报告了来自金黄色葡萄球菌的同源二聚体 EI 的 2.4A 晶体结构。EIN 由螺旋发夹 HPr 结合亚结构域和可磷酸化的βα磷酸组氨酸（P-His）结构域组成。EIC 折叠成（βα）（8）桶。EIC 的二聚体界面每单体掩埋 1833A（2）的可及表面，并包含每个二聚体的两个 Ca（2+）结合位点。金黄色葡萄球菌和大肠杆菌 EI 结构域的结构（Teplyakov，A.，Lim，K.，Zhu，P. P.，Kapadia，G.，Chen，C. C.，Schwartz，J.，Howard，A.，Reddy，P. T.，Peterkofsky，A.，和 Herzberg，O.（2006）Proc。Natl。Acad。Sci。美国 103，16218-16223）非常相似。然而，两个结构域彼此之间的取向不同。在当前结构中，P-His 结构域与 HPr 结合结构域对接，磷酸以直线方式转移到接受体 HPr 的活性位点组氨酸。在大肠杆菌结构中，P-His 结构域的磷酸组氨酸突入 EIC 的 PEP 结合位点。在金黄色葡萄球菌结构中，与 P-His 结构域接触的 HPr 结合结构域的晶体学温度因素较低，而 EIC 的温度因素较高。在大肠杆菌结构中则相反。
