ABSTRACT
Molecular masses of functional units of two components of 2, 4-dinitrophenyl-S-glutathione (DNP-SG) transport across the erythrocyte membrane determined by radiation inactivation were 437 +/- 69 kDa for the high-affinity component and 466 +/- 67 kDa for the low-affinity component. These results confirm that the multidrug resistance-associated protein (MRP) 1 is responsible for the high-affinity DNP-SG transport across the erythrocyte membrane and suggest that MRP1 exists in the membrane as a dimer. The molecular size of the low-affinity transporter is similar if not identical to that of MRP1. Moreover, while the molecular mass of the DNP-SG-ATPase activity of the erythrocyte membrane corresponds also to that of MRP (375 +/- 36 kDa), the molecular mass of the functional unit of dinitrophenol-stimulated ATPase is significantly lower (232 +/- 26 kDa), which suggests that thisactivity is linked to a different protein, perhapsaminophospholipid translocase.
Subject(s)
ATP-Binding Cassette Transporters/chemistry , Erythrocyte Membrane/chemistry , 2,4-Dinitrophenol/metabolism , ATP-Binding Cassette Transporters/metabolism , Adenosine Triphosphatases/metabolism , Adult , Biological Transport/radiation effects , Dimerization , Erythrocyte Membrane/metabolism , Erythrocyte Membrane/radiation effects , Glutathione/analogs & derivatives , Glutathione/metabolism , Humans , In Vitro Techniques , Multidrug Resistance-Associated ProteinsABSTRACT
There are no reports concerning glutathione-S-conjugates transport in prokaryotic cells, although many studies have been performed in eukaryotic systems. This study demonstrates that glutathione S-conjugates (2,4-dinitrophenyl-S-glutathione and bimane-S-glutathione) are transported also out of Escherichia coli K12 cells. This transport is inhibited by vanadate, fluoride and other inhibitors of glutathione S-conjugate transport in mammalian cells suggesting a similarity of this process to that known in eukaryotes.
Subject(s)
Bridged Bicyclo Compounds/metabolism , Escherichia coli/metabolism , Glutathione/analogs & derivatives , Biological Transport, Active/drug effects , Escherichia coli/drug effects , Fluorides/pharmacology , Glutathione/metabolism , Kinetics , Probenecid/pharmacology , Uncoupling Agents/pharmacology , Vanadates/pharmacologyABSTRACT
Pig erythrocyte membrane Mg2+-ATPase activity was stimulated by various glutathione S-conjugates. For alkyl S-conjugates, the Km for the stimulation was lower, the more hydrophobic was the conjugate. 2,4-Dinitrophenyl-S-(N-acetyl)cysteine also stimulated the Mg2+-ATPase activity, suggesting a low specificity of the ¿glutathione S-conjugate pump¿. The Km values for the stimulation by 2,4-dinitrophenyl conjugates were lower than predictable on the basis of hydrophobicity which indicates a high affinity of the transporter for these conjugates.
