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AlF4- reversibly inhibits ‘P’-type cation-transport ATPases, possibly by interacting with the phosphate-binding site of the ATPase
- Source :
- Biochemical Journal; August 1988, Vol. 253 Issue: 3 p827-833, 7p
- Publication Year :
- 1988
-
Abstract
- The only known cellular action of AlF4- is to stimulate the G-proteins. The aim of the present work is to demonstrate that AlF4- also inhibits ‘P’-type cation-transport ATPases. NaF plus AlCl3 completely and reversibly inhibits the activity of the purified (Na+ + K+)-ATPase (Na+- and K+-activated ATPase) and of the purified plasmalemmal (Ca2+ + Mg2+)-ATPase (Ca2+-stimulated and Mg2+-dependent ATPase). It partially inhibits the activity of the sarcoplasmic-reticulum (Ca2+ + Mg2+)-ATPase, whereas it does not affect the mitochondrial H+-transporting ATPase. The inhibitory substances are neither F- nor Al3+ but rather fluoroaluminate complexes. Because AlF4- still inhibits the ATPase in the presence of guanosine 5′-[beta-thio]diphosphate, and because guanosine 5′-[beta gamma-imido]triphosphate does not inhibit the ATPase, it is unlikely that the inhibition could be due to the activation of an unknown G-protein. The time course of inhibition and the concentrations of NaF and AlCl3 required for this inhibition differ for the different ATPases. AlF4- inhibits the (Na+ + K+)-ATPase and the plasmalemmal (Ca2+ + Mg2+)-ATPase noncompetitively with respect to ATP and to their respective cationic substrates, Na+ and Ca2+. AlF4- probably binds to the phosphate-binding site of the ATPase, as the Ki for inhibition of the (Na+ + K+)-ATPase and of the plasmalemmal (Ca2+ + Mg2+)-ATPase is shifted in the presence of respectively 5 and 50 mM-Pi to higher concentrations of NaF. Moreover, AlF4- inhibits the K+-activated p-nitrophenylphosphatase of the (Na+ + K+)-ATPase competitively with respect to p-nitrophenyl phosphate. This AlF4- –induced inhibition of ‘P’-type cation-transport ATPases warns us against explaining all the effects of AlF4- on intact cells by an activation of G-proteins.
Details
- Language :
- English
- ISSN :
- 02646021 and 14708728
- Volume :
- 253
- Issue :
- 3
- Database :
- Supplemental Index
- Journal :
- Biochemical Journal
- Publication Type :
- Periodical
- Accession number :
- ejs51301904
- Full Text :
- https://doi.org/10.1042/bj2530827