Chen Kui, Yuldasheva Saodat, Penner-Hahn James E, O'Halloran Thomas V
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
J Am Chem Soc. 2003 Oct 8;125(40):12088-9. doi: 10.1021/ja036070y.
CueR is a copper-responsive genetic switch that regulates transcription of genes encoding the primary copper-exporting system in E. coli, CopA and CueO. Although a member of the MerR family of regulatory proteins, CueR has four cysteines in an array that is distinct from those in Hg(II)-sensing MerR or in Zn-sensing ZntR. A recent crystal structure showed one copper atom in CueR bound to cysteines Cys112 and Cys120 in a linear CuS2 structure, but left open the questions of whether the other half of the CueR dimer has the same structure, and of whether these structures depend on the two additional C-terminal cysteines. Metal binding, transcription runoff, and cysteine modification studies show that only Cys112 and Cys 120 are necessary and sufficient to make the transcriptionally active Cu-sensing site. X-ray absorption spectroscopy shows that this site binds Cu(I) in a strictly linear CuS2 site in solution, a structure that is rarely observed in copper proteins. This structure does not depend either on additional metal loading or upon the presence of additional C-terminal cysteine ligands and is well suited for an ultrasensitve receptor site that discriminates against the binding of other metal ions.
CueR是一种铜响应性遗传开关，可调节大肠杆菌中编码主要铜输出系统CopA和CueO的基因的转录。尽管CueR是调控蛋白MerR家族的成员，但它有四个呈特定排列的半胱氨酸，这与汞（II）感应MerR或锌感应ZntR中的半胱氨酸排列不同。最近的晶体结构显示，CueR中的一个铜原子以线性CuS2结构与半胱氨酸Cys112和Cys120结合，但留下了两个问题：CueR二聚体的另一半是否具有相同结构，以及这些结构是否依赖于另外两个C末端半胱氨酸。金属结合、转录延伸和半胱氨酸修饰研究表明，只有Cys112和Cys120对于形成转录活性铜感应位点是必要且充分的。X射线吸收光谱表明，该位点在溶液中以严格线性的CuS2位点结合Cu（I），这种结构在铜蛋白中很少见。这种结构既不依赖于额外的金属负载，也不依赖于额外的C末端半胱氨酸配体的存在，非常适合作为一个超敏感的受体位点来区分其他金属离子的结合。
