title: Functional response of the small multidrug resistance protein EmrE to mutations in transmembrane helix 2.
abstract: Escherichia coli EmrE is a small multidrug resistance protein encompassing four transmembrane (TM) sequences that oligomerizes to confer resistance to antimicrobials. Here we examined the effects on in vivo protein accumulation and ethidium resistance activity of single residue substitutions at conserved and variable positions in EmrE transmembrane segment 2 (TM2). We found that activity was reduced when conserved residues localized to one TM2 surface were replaced. Our findings suggest that conserved TM2 positions tolerate greater residue diversity than conserved sites in other EmrE TM sequences, potentially reflecting a source of substrate polyspecificity.
authors.affiliation: Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1A8, Canada.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada.
authors.forename: Arianna
authors.initials: A
authors.lastname: Rath
authors.affiliation: Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1A8, Canada. Electronic address: deber@sickkids.ca.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Deber
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017920:Antiporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D017124:Conserved Sequence; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004996:Ethidium / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D013379:Substrate Specificity
chemical_list: D017920:Antiporters; D029968:Escherichia coli Proteins; C075436:EmrE protein, E coli; D004996:Ethidium
keywords: Bacterial multidrug resistance; Polyspecificity; Residue variability; Sequence conservation; Small multidrug resistance protein; Transmembrane helix