Periplasmic metal-resistance protein CusF exhibits high affinity and specificity for both CuI and AgI

Joshua T. Kittleson, Isabell R. Loftin, Andrew C. Hausrath, Kevin P. Engelhardt, Christopher Rensing, Megan M. McEvoy

Research output: Contribution to journalArticle

53 Scopus citations

Abstract

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

Original languageEnglish (US)
Pages (from-to)11096-11102
Number of pages7
JournalBiochemistry
Volume45
Issue number37
DOIs
StatePublished - Sep 19 2006

ASJC Scopus subject areas

  • Biochemistry

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