Loftin Isabell R, Franke Sylvia, Blackburn Ninian J, McEvoy Megan M
Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, USA.
Protein Sci. 2007 Oct;16(10):2287-93. doi: 10.1110/ps.073021307.
Elevated levels of copper or silver ions in the environment are an immediate threat to many organisms. Escherichia coli is able to resist the toxic effects of these ions through strictly limiting intracellular levels of Cu(I) and Ag(I). The CusCFBA system is one system in E. coli responsible for copper/silver tolerance. A key component of this system is the periplasmic copper/silver-binding protein, CusF. Here the X-ray structure and XAS data on the CusF-Ag(I) and CusF-Cu(I) complexes, respectively, are reported. In the CusF-Ag(I) structure, Ag(I) is coordinated by two methionines and a histidine, with a nearby tryptophan capping the metal site. EXAFS measurements on the CusF-Cu(I) complex show a similar environment for Cu(I). The arrangement of ligands effectively sequesters the metal from its periplasmic environment and thus may play a role in protecting the cell from the toxic ion.
环境中铜离子或银离子水平的升高对许多生物体构成直接威胁。大肠杆菌能够通过严格限制细胞内铜（I）和银（I）的水平来抵抗这些离子的毒性作用。CusCFBA系统是大肠杆菌中负责铜/银耐受性的一个系统。该系统的一个关键成分是周质铜/银结合蛋白CusF。本文分别报道了CusF-Ag（I）和CusF-Cu（I）配合物的X射线结构和XAS数据。在CusF-Ag（I）结构中，Ag（I）由两个甲硫氨酸和一个组氨酸配位，附近的一个色氨酸覆盖金属位点。对CusF-Cu（I）配合物的EXAFS测量显示Cu（I）具有相似的环境。配体的排列有效地将金属与其周质环境隔离，因此可能在保护细胞免受有毒离子侵害方面发挥作用。
