Labeling of the Amphiuma erythrocyte K+/H+ exchanger with H2DIDS.
Subsequent to swelling, the Amphiuma red blood cells lose K+, Cl-, and water until normal cell volume is restored. Net solute loss is the result of K+/H+ and Cl-/HCO3- exchangers functionally coupled through changes in pH and therefore HCO3-. Whereas the Cl-/HCO3- exchanger is constitutively active, K+/H+ actively is induced by cell swelling. The constitutive Cl-/HCO3- exchanger is inhibited by low concentrations (< 1 microM) of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) or H2DIDS, yet the concentration of H2DIDS > 25 microM irreversibly modifies the K+/H+ exchanger in swollen cells. We exploited the volume-dependent irreversible low-affinity reaction between H2DIDS and the K+/H+ to identify the protein(s) associated with K+/H+ exchange activity. Labeling of the membrane proteins of intact cells with 3H2DIDS results in high-affinity labeling of a broad 100-kDa band, thought to be the anion exchanger. Additional swelling-dependent low-affinity labeling at 110 kDa suggests the possibility of a volume-induced population of anion exchangers. Finally, the correlation between volume-sensitive K+/H+ modification and low-affinity labeling suggests that transport activity is associated with a protein of approximately 85 kDa. Although a 55-kDa protein is also labeled, it is a less likely candidate, since label incorporation and transport modification are less well correlated than that of the 85- and 110-kDa proteins.
Maldonado
H M
HM
Department of Human Physiology, University of California at Davis, School of Medicine 95616.
Cala
P M
PM
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000378:metabolism; D017920:Antiporters / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007474:Ion Exchange; D008565:Membrane Proteins / Q000097:blood; D027961:Potassium-Hydrogen Antiporters; D012964:Sodium / Q000378:metabolism; D013997:Time Factors; D014562:Caudata / Q000097:blood*
D000838:Anions; D017920:Antiporters; D008565:Membrane Proteins; D027961:Potassium-Hydrogen Antiporters; C018564:dihydro-DIDS; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid