Identification of the ABC protein SapD as the subunit that confers ATP dependence to the K+-uptake systems Trk(H) and Trk(G) from Escherichia coli K-12
|ABC system; ANTIMICROBIAL PEPTIDES; BINDING; CHANNEL; CRYSTAL-STRUCTURE; GENETIC-ANALYSIS; GROWING CELLS; K+ transport; Kir-SUR system; Microbiology; peptide transporter family; POTASSIUM-TRANSPORT LOCI; regulation by adenine nucleotides; RESISTANCE; STOICHIOMETRY; VIBRIO-ALGINOLYTICUS
|SOC GENERAL MICROBIOLOGY
The activity of the two almost identical K+-uptake systems, Trk(H) and Trk(G), from Escherichia con K-12 depends completely and partially on the presence of the trkE gene, respectively. trkE maps inside the sapABCDF operon, which encodes an ATP-binding cassette (ABC) transporter of unknown function from the subgroup of peptide-uptake systems. This study was carried out to clarify the role of sapABCDF gene products in the ATP dependence of the E. con Trk systems. For this purpose Delta sapABCDF Delta trkG and Delta sapABCDF Delta trkH strains of E. con containing plasmids with sap genes from either E. con or Vibrio alginolyticus were used. All five plasmid-encoded E. con Sap proteins were made in E. con mini-cells. The presence of the ATP-binding SapD protein from either E. con or V. alginolyticus alone was sufficient for stimulating the K+ transport activity of the Trk(H) and TrkG systems. K+-uptake experiments with Escherichia con cells containing SapD variants with changes in the Walker A box Lys-46 residue, the Walker B box Asp-183 residue and the signature motif residues Gly-162 or Gln-165 suggested that adenine nucleotide binding to SapD rather than ATP hydrolysis by this subunit is required for the activity of the E. con Trk(H) system. K+ transport via two plasmid-encoded Trk systems in a Delta sapABCDF E. con strain remained dependent on both a high membrane potential and a high cytoplasmic ATP concentration, indicating that in E. con ATP dependence of Trk activity can be independent of Sap proteins. These data are interpreted to mean that Trk systems can interact with an ABC protein other than SapD.
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checked on Mar 2, 2024