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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structure of phosphorylated enzyme Ⅰ, the phosphoenolpyruvate:sugar phosphotransferase system sugar translocation signal protein
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Structure of phosphorylated enzyme Ⅰ, the phosphoenolpyruvate:sugar phosphotransferase system sugar translocation signal protein

机译：磷酸化酶Ⅰ的结构，磷酸烯醇丙酮酸：糖磷酸转移酶系统糖转运信号蛋白

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摘要

Bacterial transport of many sugars, coupled to their phosphoryla-tion, is carried out by the phosphoenolpyruvate (PEP)isugar phosphotransferase system and involves five phosphoryl group transfer reactions. Sugar translocation initiates with the Mg~(2+)-dependent phosphorylation of enzyme Ⅰ (EI) by PEP. Crystals of Escherichia coli EI were obtained by mixing the protein with Mg~(2+) and PEP, followed by oxalate, an EI inhibitor. The crystal structure reveals a dimeric protein where each subunit comprises three domains: a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr; a domain that carries the phosphorylated histidine residue, His-189; and a PEP-binding domain. The PEP-binding site is occupied by Mg~(2+) and oxalate, and the phosphorylated His-189 is in-line for phosphotransfer to/from the ligand. Thus, the structure represents an enzyme intermediate just after phosphotransfer from PEP and before a conformational transition that brings His-189～P in proximity to the phosphoryl group acceptor, His-15 of HPr. A model of this conformational transition is proposed whereby swiveling around an α-helical linker disengages the His domain from the PEP-binding domain. Assuming that HPr binds to the HPr-binding domain as observed by NMR spectroscopy of an EI fragment, a rotation around two linker segments orients the His domain relative to the HPr-binding domain so that His-189～P and His-15 are appropriately stationed for an in-line phosphotransfer reaction.
机译：许多糖的细菌转运及其磷酸化是通过磷酸烯醇丙酮酸（PEP）异糖磷酸转移酶系统进行的，涉及五个磷酸基转移反应。糖易位是由PEP引起的酶Ⅰ（EI）的Mg〜（2+）依赖性磷酸化作用开始的。通过将蛋白质与Mg〜（2+）和PEP混合，然后混合EI抑制剂草酸盐，可以得到大肠杆菌EI的晶体。晶体结构揭示了一种二聚体蛋白，其中每个亚基包含三个域：一个与伴侣PEP：糖磷酸转移酶系统蛋白HPr结合的域；带有磷酸化的组氨酸残基His-189的结构域；和PEP绑定域。 PEP结合位点被Mg〜（2+）和草酸盐占据，并且磷酸化的His-189在线发生向/从配体的磷酸转移。因此，该结构代表了从PEP进行磷转移后到构象转变之前的酶中间体，该构象转变使His-189〜P接近磷酸基受体HPr的His-15。提出了这种构象转变的模型，其中围绕α-螺旋接头的旋转使His结构域与PEP结合结构域脱离。假设通过EI片段的NMR光谱观察到HPr与HPr结合结构域结合，围绕两个接头片段的旋转使His结构域相对于HPr结合结构域取向，使得His-189〜P和His-15合适进行在线磷酸转移反应。

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