title: NIP- and NAP-taurine bind to external modifier site of AE1 (band 3), at which iodide inhibits anion exchange.
abstract: External iodide (I-o) inhibits AE1 (band 3)-mediated anion exchange in human red blood cells by binding to a noncompetitive inhibitory site, the external halide modifier site. External N-(4-azido-2-nitrophenyl)-2-aminoethyl sulfonate (NAP-taurine) and N-(4-isothiocyano-2-nitrophenyl)-2-aminoethyl sulfonate (NIP-taurine) also inhibit Cl- exchange noncompetitively. Increasing I-o decreases the inhibitory potency of NIP-taurine in a competitive fashion; this effect is not due to I- binding to the transport site, which has little effect on the NIP-taurine affinity. Bis(sulfosuccinimidyl)-suberate (BSSS) abolishes the noncompetitive inhibitory effect of I-o and greatly reduces the inhibitory effect of NAP-taurine. Together with previous work, these data suggest that external halides, such as I-, Br-, and probably also Cl-, bind to the same noncompetitive inhibitory site as do NAP- and NIP-taurine and that these reagents can be used to label the halide modifier site. Lys-539, a probable reaction site of BSSS, lies within the same segment of AE1 that is labeled by NAP-taurine and thus may be part of the modifier site.
authors.affiliation: Department of Biophysics, University of Rochester School of Medicine, New York 14642, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Knauf
authors.forename: L J
authors.initials: LJ
authors.lastname: Spinelli
mesh_terms: D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D000838:Anions / Q000378:metabolism*; D001692:Biological Transport; D003432:Cross-Linking Reagents / Q000494:pharmacology; D006801:Humans; D007454:Iodides / Q000494:pharmacology*; D007474:Ion Exchange; D009994:Osmolar Concentration; D013388:Succinimides / Q000494:pharmacology; D013654:Taurine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D000838:Anions; D003432:Cross-Linking Reagents; D007454:Iodides; D013388:Succinimides; C054251:N-(4-isothiocyano-2-nitrophenyl)-2-aminoethanesulfonate; D013654:Taurine; C010861:NAP taurine; C035760:bis(sulfosuccinimidyl)suberate