Mutant Phe788➝Leu of the Na+,K+-ATPase is inhibited by micromolar concentrations of potassium and exhibits high Na+-ATPase activity at low sodium concentrations
| العنوان: | Mutant Phe788➝Leu of the Na+,K+-ATPase is inhibited by micromolar concentrations of potassium and exhibits high Na+-ATPase activity at low sodium concentrations |
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| المؤلفون: | Bente Vilsen |
| المصدر: | Vilsen, B 1999, ' Mutant Phe788➝Leu of the Na +,K +-ATPase is inhibited by micromolar concentrations of potassium and exhibits high Na +-ATPase activity at low sodium concentrations ' Biochemistry, bind 38, s. 11389-11400 . Vilsen, B 1999, ' Mutant Phe788→Leu of the Na +,K +-ATPase is inhibited by micromolar concentrations of potassium and exhibits high Na +-ATPase activity at low sodium concentrations ', Biochemistry, vol. 38, pp. 11389-11400 . |
| سنة النشر: | 1999 |
| مصطلحات موضوعية: | Phenylalanine, Potassium, Mutant, chemistry.chemical_element, Kidney, Transfection, Biochemistry, Medicinal chemistry, Ouabain, Dephosphorylation, Adenosine Triphosphate, Leucine, ATP hydrolysis, medicine, Animals, Phosphorylation, Na+/K+-ATPase, 4-Nitrophenylphosphatase, Dose-Response Relationship, Drug, Chemistry, Sodium, Recombinant Proteins, Rats, Turnover number, Enzyme Activation, COS Cells, Sodium-Potassium-Exchanging ATPase, medicine.drug, Low sodium |
| الوصف: | Mutant Phe788 --> Leu of the rat kidney Na+,K(+)-ATPase was expressed in COS cells to active-site concentrations between 40 and 60 pmol/mg of membrane protein. Analysis of the functional properties showed that the discrimination between Na+ and K+ on the two sides of the system is severely impaired in the mutant. Micromolar concentrations of K+ inhibited ATP hydrolysis (K(0.5) for inhibition 107 microM for the mutant versus 76 mM for the wild-type at 20 mM Na+), and at 20 mM K+, the molecular turnover number for Na+,K(+)-ATPase activity was reduced to 11% that of the wild-type. This inhibition was counteracted by Na+ in high concentrations, and in the total absence of K+, the mutant catalyzed Na(+)-activated ATP hydrolysis ("Na(+)-ATPase activity") at an extraordinary high rate corresponding to 86% of the maximal Na+,K(+)-ATPase activity. The high Na(+)-ATPase activity was accounted for by an increased rate of K(+)-independent dephosphorylation. Already at 2 mM Na+, the dephosphorylation rate of the mutant was 8-fold higher than that of the wild-type, and the maximal rate of Na(+)-induced dephosphorylation amounted to 61% of the rate of K(+)-induced dephosphorylation. The cause of the inhibitory effect of K+ on ATP hydrolysis in the mutant was an unusual stability of the K(+)-occluded E2(K2) form. Hence, when E2(K2) was formed by K+ binding to unphosphorylated enzyme, the K(0.5) for K+ occlusion was close to 1 microM in the mutant versus 100 microM in the wild-type. In the presence of 100 mM Na+ to compete with K+ binding, the K(0.5) for K+ occlusion was still 100-fold lower in the mutant than in the wild-type. Moreover, relative to the wild-type, the mutant exhibited a 6-7-fold reduced rate of release of occluded K+, a 3-4-fold increased apparent K+ affinity in activation of the pNPPase reaction, a 10-11-fold lower apparent ATP affinity in the Na+,K(+)-ATPase assay with 250 microM K+ present (increased K(+)-ATP antagonism), and an 8-fold reduced apparent ouabain affinity (increased K(+)-ouabain antagonism). |
| اللغة: | Danish |
| الوصول الحر: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a3c1db90c90cb8ad1145d4b04b54e64aTest https://pure.au.dk/portal/da/publications/mutant-phe788leu-of-the-nakatpase-is-inhibited-by-micromolar-concentrations-of-potassium-and-exhibits-high-naatpase-activity-at-low-sodium-concentrationsTest(3a3219b0-955d-11da-bee9-02004c4f4f50).html |
| حقوق: | RESTRICTED |
| رقم الانضمام: | edsair.doi.dedup.....a3c1db90c90cb8ad1145d4b04b54e64a |
| قاعدة البيانات: | OpenAIRE |
| الوصف غير متاح. |