title: A bacterial glutathione transporter (Escherichia coli CydDC) exports reductant to the periplasm.
abstract: Glutathione (GSH), a major biological antioxidant, maintains redox balance in prokaryotes and eukaryotic cells and forms exportable conjugates with compounds of pharmacological and agronomic importance. However, no GSH transporter has been characterized in a prokaryote. We show here that a heterodimeric ATP-binding cassette-type transporter, CydDC, mediates GSH transport across the Escherichia coli cytoplasmic membrane. In everted membrane vesicles, GSH is imported via an ATP-driven, protonophore-insensitive, orthovanadate-sensitive mechanism, equating with export to the periplasm in intact cells. GSH transport and cytochrome bd quinol oxidase assembly are abolished in the cydD1 mutant. Glutathione disulfide (GSSG) was not transported in either Cyd(+) or Cyd(-) strains. Exogenous GSH restores defective swarming motility and benzylpenicillin sensitivity in a cydD mutant and also benzylpenicillin sensitivity in a gshA mutant defective in GSH synthesis. Overexpression of the cydDC operon in dsbD mutants defective in disulfide bond formation restores dithiothreitol tolerance and periplasmic cytochrome b assembly, revealing redundant pathways for reductant export to the periplasm. These results identify the first prokaryotic GSH transporter and indicate a key role for GSH in periplasmic redox homeostasis.
authors.affiliation: Department of Molecular Biology and Biotechnology, Firth Court, The University of Sheffield, UK.
authors.forename: Marc S
authors.initials: MS
authors.lastname: Pittman
authors.forename: Hilary C
authors.initials: HC
authors.lastname: Robinson
authors.forename: Robert K
authors.initials: RK
authors.lastname: Poole
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry; D045303:Cytochromes b / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D045222:Electron Transport Chain Complex Proteins / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism*; D006706:Homeostasis; D007785:Lactose / Q000378:metabolism; D026901:Membrane Transport Proteins; D008954:Models, Biological; D009154:Mutation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry; D010100:Oxygen / Q000378:metabolism; D010400:Penicillin G / Q000494:pharmacology; D019897:Periplasm / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors; D014638:Vanadates / Q000494:pharmacology
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; C089838:CydC protein, E coli; C089839:CydD protein, E coli; D003573:Cytochrome b Group; D003580:Cytochromes; D004220:Disulfides; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C086860:glutathione transporter; D014638:Vanadates; D045303:Cytochromes b; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; D005978:Glutathione; D007785:Lactose; D010400:Penicillin G; D010100:Oxygen