Periplasmic Metal-Resistance Protein CusF Exhibits High Affinity and Specificity for Both CuI and AgI

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• 作者：Joshua T. Kittleson ; Isabell R. Loftin ; Andrew C. Hausrath ; Kevin P. Engelhardt ; Christopher Rensing ; Megan M. McEvoy
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：September 19, 2006
• 年：2006
• 卷：45
• 期：37
• 页码：11096 - 11102
• 全文大小：158K
• 年卷期：v.45,no.37(September 19, 2006)
• ISSN：1520-4995

文摘

The periplasmic protein CusF, as a part of the CusCFBA efflux complex, plays a role inresistance to elevated levels of copper and silver in Escherichia coli. Although homologues have beenidentified in other Gram-negative bacteria, the substrate of CusF and its precise role in metal resistancehave not been described. Here, isothermal titration calorimetry (ITC) was used to demonstrate that CusFbinds with high affinity to both Cu^I and Ag^I but not Cu^II. The affinity of CusF for Ag^I was higher thanthat for Cu^I, which could reflect more efficient detoxification of Ag^I given the lack of a cellular need forAg^I. The chemical shifts in the nuclear magnetic resonance (NMR) spectra of CusF-Ag^I as compared toapo-CusF show that the region of CusF most affected by Ag^I binding encompasses three absolutelyconserved residues: H36, M47, and M49. This suggests that these residues may play a role in Ag^Icoordination. The NMR spectra of CusF in the presence of Cu^II do not indicate specific binding, whichis in agreement with the ITC data. We conclude that Cu^I and Ag^I are the likely physiological substrates.