Occlusion of K+ in the Na+/K+/2Cl− cotransporter of Ehrlich ascites tumor cells
| Autor: | Else K. Hoffmann, Thomas Krarup, Bo Skaaning Jensen |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Sodium-Potassium-Chloride Symporters
Cytochalasin B Stereochemistry ATPase Ion chromatography Membrane vesicle Biophysics Medicinal chemistry Biochemistry Ouabain chemistry.chemical_compound Ion binding n-Octyl glucoside Tumor Cells Cultured medicine Animals Binding site Carcinoma Ehrlich Tumor Bumetanide Ion Transport biology Occlusion Chemistry Cell Membrane Cell Biology Potassium biology.protein Carrier Proteins Cotransporter Na+/K+/2Cl− cotransporter medicine.drug |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Biomembranes. 1284(1):97-108 |
| ISSN: | 0005-2736 |
| DOI: | 10.1016/0005-2736(96)00120-4 |
| Popis: | Proteins of n-octyl glycoside solubilized membrane vesccles derived from Ehrlich ascites tumor cells can occlude 86 Rb + . K + displaces 86 Rb + and it is assumed that 86 Rb + can be used as a tracer to measure K + occlusion. The following observations indicate that the Na + /K + /2Cl − cotransporter is responsible for this occlusion: (1) Na + does not compete for the K + binding site, but rather stimulates 86 Rb + occlusion. (2) K + occlusion saturates with increasing [Na + ] and [K + ], the respective K 0.5 values being 50 ± 7 μM for Na + and 371 ± 63 μM for K + . (3) Preincubation with 1 mM ouabain does not inhibit 86 Rb + occlusion, arguing against the Na + /K + -ATPase as being responsible for the occlusion. This notion is supported by the K 0.5 value for K + being higher than reported for Na + /K + -ATPase and by the stimulatory effect of Na + . (4) The K + occlusion is sensitive to [Cl − ], and the occluded ion is protected by the presence of bumetanide during cation exchange chromatography. Our results suggest that occlusion measurements of substrate ions could be a profitable way to study the ion binding mechanism(s) of the Na + /K + /2Cl − cotransporter. |
| Databáze: | OpenAIRE |
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