Differential effect of pH on sodium binding by the various GABA transporters expressed in Xenopus oocytes.
Mouse GABA transporters belong to the family of Na(+)- and Cl(-)-dependent neurotransmitter transporters. The four GABA transporters exhibit unique presteady-state currents when expressed in Xenopus oocytes. The properties of the presteady-state currents correspond to their different affinities to Na(+). In the presence of 20 microM GABA and at pH 7.5, the half-maximal uptake activity was 47, 120, 25 and 35 mM Na(+) for GAT1, GAT2, GAT3 and GAT4, respectively. The appearance of presteady-state currents at positive or negative imposed potentials was in correlation with the affinity to Na(+). Changing the external pH differentially affected the GABA uptake and the presteady-state activities of the various GABA transporters. It is suggested that protons compete with Na(+) on its binding site; however, the proton binding is not productive and is unable to drive GABA uptake.
Grossman
Tamar R
TR
Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel.
Nelson
Nathan
N
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004594:Electrophysiology / Q000379:methods; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D050485:GABA Plasma Membrane Transport Proteins; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009865:Oocytes / Q000378:metabolism*; D027361:Organic Anion Transporters; D012964:Sodium / Q000378:metabolism*
D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; D012964:Sodium; C079264:Slc6a11 protein, mouse; C493414:Slc6a1 protein, mouse; C490439:Slc6a12 protein, mouse; C493419:Slc6a13 protein, mouse