Effects of the transport site conformation on the binding of external NAP-taurine to the human erythrocyte anion exchange system: evidence for intrinsic asymmetry

Journal Article · Tue May 01 04:00:00 EDT 1984 · J. Gen. Physiol.; (United States)

DOI:https://doi.org/10.1085/jgp.83.5.683· OSTI ID:6188883

Knauf, P A; Law, F Y; Tarshis, T; Furuya, W

External N-(4-azido (NAP-taurine) inhibits human red cell chloride exchange by binding to a site that is distinct from the chloride transport site. Increases in the intracellular chloride concentration (at constant external chloride) cause an increase in the inhibitory potency of external NAP-taurine. This effect is not due to the changes in pH or membrane potential that usually accompany a chloride gradient, since even when these changes are reversed or eliminated the inhibitory potency remains high. According to the ping-pong model for anion exchange, such transmembrane effects of intracellular chloride on external NAP-taurine can be explained if NAP-taurine only binds to its site when the transport site is in the outward-facing (E/sub o/ or ECl/sub o/) form. Since NAP-taurine prevents the conformational change from ECl/sub o/ to ECl/sub i/, it must lock the system in the outward-facing form. NAP-taurine can therefore be used just like the competitive inhibitor H/sub 2/DIDS (4,4'-diisothiocyano-1,2-diphenylethane-2,2'-disulfonic acid) to monitor the fraction of transport sites that face outward. A quantitative analysis of the effects of chloride gradients on the inhibitory potency of NAP-taurine and H/sub 2/DIDS reveals that the transport system is intrinsically asymmetric, such that when Cl/sub i/ = Cl/sub o/, most of the unloaded transport sites face the cytoplasmic side of the membrane. 30 references, 7 figures, 3 tables.

• Research Organization: Research Institute, Toronto, Ontario
• OSTI ID: 6188883
• Journal Information: J. Gen. Physiol.; (United States), Journal Name: J. Gen. Physiol.; (United States) Vol. 83; ISSN JGPLA
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560301* -- Chemicals Metabolism & Toxicology-- Cells-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINES
ANIONS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
DATA
ERYTHROCYTES
EXPERIMENTAL DATA
HALIDES
HALOGEN COMPOUNDS
INFORMATION
INHIBITION
ION EXCHANGE
IONS
KINETICS
MATERIALS
MATHEMATICAL MODELS
MEMBRANE TRANSPORT
MEMBRANES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PH VALUE
REACTION KINETICS
SULFONIC ACIDS
TAURINE