The external anion binding site of the human erythrocyte anion transporter: DNDS binding and competition with chloride

1982 ◽  
Vol 65 (1-2) ◽  
pp. 111-123 ◽  
Author(s):  
Otto Fröhlich
Keyword(s):  
Binding Site ◽  
Human Erythrocyte ◽  
Anion Binding ◽  
Anion Transporter

Interactions of inhibitors on anion transporter of human erythrocyte

1987 ◽  
Vol 252 (2) ◽  
pp. C153-C162 ◽  
Author(s):  
O. Frohlich ◽  
R. B. Gunn
Keyword(s):  
Binding Site ◽  
Human Erythrocyte ◽  
Binding Domain ◽  
Human Erythrocytes ◽  
Anion Binding ◽  
Chloride Binding ◽  
Protein Surface ◽  
Anion Transporter ◽  
Transport Site ◽  
Chloride Concentrations

Chloride tracer efflux was measured from intact human erythrocytes into media containing different chloride concentrations and different concentrations of the inhibitors 4,4'-dinitrostilbene-2-2'-disulfonate (DNDS), N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine), phloretin, and sulfate. The data were analyzed to test whether these inhibitors were mutually exclusive with each other or whether they could bind at the same time. Under the assumption that mutual exclusiveness is due to steric interference, the data can be used to map out the protein surface near the outward-facing anion binding-transport site. It is concluded that there are separate domains for NAP taurine and phloretin that do not overlap with each other or with the chloride binding site. These two domains do, however, overlap with the binding domain for DNDS that, in addition, excludes the binding of chloride and sulfate.

scholarly journals The human erythrocyte anion transport protein, band 3. Characterization of exofacial alkaline titratable groups involved in anion binding/translocation.

1992 ◽  
Vol 100 (2) ◽  
pp. 301-339 ◽  
Author(s):  
P J Bjerrum
Keyword(s):  
Ionic Strength ◽  
Binding Site ◽  
Transport System ◽  
Human Erythrocyte ◽  
Binding Constant ◽  
Anion Transport ◽  
High Ionic Strength ◽  
Anion Binding ◽  
Asymmetry Factor ◽  
Sensitive Group

Chloride self-exchange across the human erythrocyte membrane at alkaline extracellular pH (pHO) and constant neutral intracellular pH (pH(i)) can be described by an exofacial deprotonatable reciprocating anion binding site model. The conversion of the transport system from the neutral to the alkaline state is related to deprotonation of a positively charged ionic strength- and substrate-sensitive group. In the absence of substrate ions ([ClO] = 0) the group has a pK of approximately 9.4 at constant high ionic strength (equivalent to approximately 150 mM KCl) and a pK of approximately 8.7 at approximately zero ionic strength. The alkaline ping-pong system (examined at constant high ionic strength) demonstrates outward recruitment of the binding sites with an asymmetry factor of approximately 0.2, as compared with the inward recruitment of the transport system at neutral pHO with an asymmetry factor of approximately 10. The intrinsic half-saturation constant for chloride binding, with [Cli] = [Clo], increased from approximately 30 mM at neutral to approximately 110 mM at alkaline pHO. The maximal transport rate was a factor of approximately 1.7 higher at alkaline pHO. This increase explains the stimulation of anion transport, the "modifier hump," observed at alkaline pHO. The translocation of anions at alkaline pHO was inhibited by deprotonation of another substrate-sensitive group with an intrinsic pK of approximately 11.3. This group together with the group with a pK of approximately 9.4 appear to form the essential part of the exofacial anion binding site. The effect of extracellular iodide inhibition on chloride transport as a function of pHO could, moreover, be simulated if three extracellular iodide binding constants were included in the model: namely, a competitive intrinsic iodide binding constant of approximately 1 mM in the neutral state, a self-inhibitor binding constant of approximately 120 mM in the neutral state, and a competitive intrinsic binding constant of approximately 38 mM in the alkaline state.

scholarly journals Mapping the ankyrin-binding site of the human erythrocyte anion exchanger

1989 ◽  
Vol 264 (16) ◽  
pp. 9665-9672 ◽  
Author(s):  
L Davis ◽  
S E Lux ◽  
V Bennett
Keyword(s):  
Binding Site ◽  
Anion Exchanger ◽  
Human Erythrocyte

scholarly journals The aldolase-binding site of the human erythrocyte membrane is at the NH2 terminus of band 3.

1981 ◽  
Vol 256 (21) ◽  
pp. 11203-11208 ◽  
Author(s):  
S.N. Murthy ◽  
T. Liu ◽  
R.K. Kaul ◽  
H. Köhler ◽  
T.L. Steck
Keyword(s):  
Binding Site ◽  
Erythrocyte Membrane ◽  
Human Erythrocyte ◽  
Band 3 ◽  
Human Erythrocyte Membrane

scholarly journals Mouse Bestrophin-2 Is a Bona fide Cl− Channel

2004 ◽  
Vol 123 (4) ◽  
pp. 327-340 ◽  
Author(s):  
Zhiqiang Qu ◽  
Rodolphe Fischmeister ◽  
Criss Hartzell
Keyword(s):  
Binding Site ◽  
Cell Lines ◽  
Electrostatic Interactions ◽  
Anion Binding ◽  
Wild Type ◽  
Cl Channel ◽  
Mammalian Cell Lines ◽  
Conduction Pathway ◽  
Bona Fide ◽  
Cl Conductance

Bestrophins have recently been proposed to comprise a new family of Cl− channels. Our goal was to test whether mouse bestrophin-2 (mBest2) is a bona fide Cl− channel. We expressed mBest2 in three different mammalian cell lines. mBest2 was trafficked to the plasma membrane as shown by biotinylation and immunoprecipitation, and induced a Ca2+-activated Cl− current in all three cell lines (EC50 for Ca2+ = 230 nM). The permeability sequence was SCN−: I−: Br−: Cl−: F− (8.2: 1.9: 1.4: 1: 0.5). Although SCN− was highly permeant, its conductance was ∼10% that of Cl− and SCN− blocked Cl− conductance (IC50 = 12 mM). Therefore, SCN− entered the pore more easily than Cl−, but bound more tightly than Cl−. Mutations in S79 altered the relative permeability and conductance for SCN− as expected if S79 contributed to an anion binding site in the channel. PSCN/PCl = 8.2 ± 1.3 for wild-type and 3.9 ± 0.4 for S79C. GSCN/GCl = 0.14 ± 0.03 for wild-type and 0.94 ± 0.04 for S79C. In the S79 mutants, SCN− did not block Cl− conductance. This suggested that the S79C mutation altered the affinity of an anion binding site for SCN−. Additional evidence that S79 was located in the conduction pathway was provided by the finding that modification of the sulfhydryl group in S79C with MTSET+ or MTSES− increased conductance significantly. Because the effect of positively and negatively charged MTS reagents was similar, electrostatic interactions between the permeant anion and the channel at this residue were probably not critical in anion selectivity. These data provide strong evidence that mBest2 forms part of the novel Cl− conduction pathway in mBest2-transfected cells and that S79 plays an important role in anion binding in the pore of the channel.

Mapping the tropomyosin isoform 5 binding site on human erythrocyte tropomodulin: Further insights into E-Tmod/TM5 interaction

2005 ◽  
Vol 444 (2) ◽  
pp. 130-138 ◽  
Author(s):  
Carlos Vera ◽  
Jianmin Lao ◽  
Donald Hamelberg ◽  
Lanping Amy Sung
Keyword(s):  
Binding Site ◽  
Human Erythrocyte
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