title: The tfdK gene product facilitates uptake of 2,4-dichlorophenoxyacetate by Ralstonia eutropha JMP134(pJP4).
abstract: Uptake of 2,4-dichlorophenoxyacetate (2,4-D) by Ralstonia eutropha JMP134(pJP4) was studied and shown to be an energy-dependent process. The uptake system was inducible with 2,4-D and followed saturation kinetics in a concentration range of up to 60 microM, implying the involvement of a protein in the transport process. We identified an open reading frame on plasmid pJP4, which was designated tfdK, whose translation product TfdK was highly hydrophobic and showed resemblance to transport proteins of the major facilitator superfamily. An interruption of the tfdK gene on plasmid pJP4 decimated 2,4-D uptake rates, which implies a role for TfdK in uptake. A tfdA mutant, which was blocked in the first step of 2,4-D metabolism, still took up 2,4-D. A mathematical model describing TfdK as an active transporter at low micromolar concentrations fitted the observed uptake data best.
authors.affiliation: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Dübendorf.
authors.forename: J H
authors.initials: JH
authors.lastname: Leveau
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder
authors.forename: J R
authors.initials: JR
authors.lastname: van der Meer
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D000421:Alcaligenes / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D010957:Plasmids; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; C111945:TfdK protein, Ralstonia eutropha; D015084:2,4-Dichlorophenoxyacetic Acid