title: Uncoupler resistance in Escherichia coli: the role of cellular respiration.
abstract: Bioenergetic properties of a mutant strain of Escherichia coli K12 designated TUV, which is resistant to the protonophoric uncoupling agent 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidiazole (TTFB) have been compared with those of its non-resistant parent, E. coli K12 Doc-S. Strain TUV grew and respired some 20-30% faster than strain Doc-S, and was cross-resistant to carbonylcyanide p-(trifluoromethoxy)phenylhydrazone and triphenyltin, but not to 2,4-dinitrophenol. Phosphorus nuclear magnetic resonance demonstrated the TTFB-mediated collapse of the transmembrane pH gradient at identical rates in starved cells of both strains, indicating that uncoupler access and function were unimpaired in the mutant under these conditions. Strain TUV displayed enhanced uncoupler resistance and maintained intracellular pH and ATP levels only when respiring. On the other hand, strain TUV also showed increased resistance to novobiocin, implying that its outer wall permeability had been lowered. We suggest that the active resistance of strain TUV results from the exclusion of uncoupler by the interaction of inner and outer membrane components in a manner modulated by the degree of cellular energization.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: P G
authors.initials: PG
authors.lastname: Quirk
authors.forename: M R
authors.initials: MR
authors.lastname: Jones
authors.forename: R S
authors.initials: RS
authors.lastname: Haworth
authors.forename: R B
authors.initials: RB
authors.lastname: Beechey
authors.forename: I D
authors.initials: ID
authors.lastname: Campbell
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001562:Benzimidazoles / Q000378:metabolism / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D004734:Energy Metabolism / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D009675:Novobiocin / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D014475:Uncoupling Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: D001562:Benzimidazoles; D014475:Uncoupling Agents; D009675:Novobiocin; C005817:4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole; D000255:Adenosine Triphosphate