title: SMR proteins SugE and EmrE bind ligand with similar affinity and stoichiometry.
abstract: Suppressor of a groEL mutation protein E (SugE) is a small multidrug resistance (SMR) homologue. In comparison with other SMR proteins, SugE promotes bacterial resistance to a narrow range of quaternary ammonium compounds (QACs). Isothermal titration calorimetry was used to study the binding of QACs to Escherichia coli SugE in different membrane mimetic environments. In this study, the binding stoichiometry of SugE to drug was found to be 1:1, and the binding of SugE to drug was observed with the dissociation constant (K(D)) in the micromolar range for each of the drugs in the membrane mimetic environments explored. This interaction appears to be enthalpy-driven with enthalpies of 8-12 kcal/mol for each of the drugs. These results are similar to those found with drug binding to the SMR protein EmrE in an earlier study.
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, Alta., Canada T2N 1N4.
authors.forename: Curtis W
authors.initials: CW
authors.lastname: Sikora
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Turner
mesh_terms: D000595:Amino Acid Sequence; D017920:Antiporters / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D018432:Drug Resistance, Multiple; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D013816:Thermodynamics; D017186:Titrimetry
chemical_list: D017920:Antiporters; D029968:Escherichia coli Proteins; D008024:Ligands; D008565:Membrane Proteins; D018832:Molecular Chaperones; C080403:sugE protein, E coli; C075436:EmrE protein, E coli