The oxalate/sulfate antiporter in lobster hepatopancreas: internal and external binding constants.
Utilizing a purified basolateral plasma membrane vesicle (BLMV) preparation containing a sulfate/oxalate antiporter, it was demonstrated that sulfate exhibited similar binding characteristics to the transporter whether bound internally or externally. It was also demonstrated that oxalate had similar binding characteristics to the antiporter whether it was bound internally or externally. Oxalate had a greater affinity to the transporter than did sulfate. Several organic anions affected binding and, therefore, overall transport by the antiporter. Most notably, sulfate was the only anion that stimulated oxalate uptake into BLMVs, which suggests a conservative binding specificity for the antiporter. 4-Acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) and/or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) inhibited the transport rate, confirming the existence of oxalate/sulfate exchange by the transporter. These results suggest that oxalate, not sulfate, regulates the transport rate because of its greater affinity to the transporter.
Gerencser
G A
GA
Department of Physiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA. gag@phys.med.ufl.edu
Burgin
C
C
Robbins
F
F
Ahearn
G A
GA
D000818:Animals; D027321:Anion Transport Proteins; D017920:Antiporters / Q000493:pharmacokinetics*; D001639:Bicarbonates / Q000493:pharmacokinetics*; D001665:Binding Sites; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D004064:Digestive System / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D008432:Mathematical Computing; D008121:Nephropidae / Q000378:metabolism*; D010070:Oxalates / Q000493:pharmacokinetics*; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism; D000076988:Sulfate Transporters; D013431:Sulfates / Q000493:pharmacokinetics*
D027321:Anion Transport Proteins; D017920:Antiporters; D001639:Bicarbonates; D010070:Oxalates; C056459:Slc26a1 protein, rat; D000076988:Sulfate Transporters; D013431:Sulfates