EurekaMag.com logo
+ Site Statistics
References:
52,725,316
Abstracts:
28,411,598
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on Google+Follow on Google+
Follow on LinkedInFollow on LinkedIn

+ Translate

Electrophorus electricus sodium potassium atpase ec 3.6.1.3 evidence for simultaneous sodium and potassium binding in the presence of lead


Journal of Biological Chemistry 255(9): 3935-3943
Electrophorus electricus sodium potassium atpase ec 3.6.1.3 evidence for simultaneous sodium and potassium binding in the presence of lead
The effects of Na+, K+ and MgCl2 on steady state levels of phosphorylation of E. electricus electroplax (Na+ + K+)-ATPase are studied with and without Pb2+. Pb2+ stimulates enzyme phosphorylation in the absence of Na+ while inhibiting hydrolysis activity (Siegel, G.J., and Fogt, S.K. Pb2+ may be a useful probe in studying the interaction of Na+ with other ligands by their effects on phosphoenzyme. In the presence of Pb2+ and 3 mM MgCl2, phosphorylation levels are reduced only by including Na+ and K+, and not either cation alone. The phosphorylation is in a steady state at all concentrations of Na+ and K+ used and is reduced by Na+ plus K+ to the same levels in the presence of Pb2+ as found when turnover is maximal in the absence of Pb2+. A model based on simultaneous binding of Na+ and K+ to Pb .cntdot. enzyme is the only compatible possibility considered. K+ increases [MgCl2]0.5 as measured by phosphorylation in the presence of Pb2+. The competitive inhibition is completely overcome by 3 mM MgCl2. Inclusion of 100 mM Na+ completely prevents the change in [MgCl2]0.5 produced by K+, but permits a noncompetitive type of inhibition produced by Na+ plus K+ that is only partially relieved by increasing MgCl2. Two kinetically distinguished loci for Na+-K+ interactions apparently determine the steady state level of phosphorylation: one at which K+ is antagonistic to Na+ and Mg2+ (or MgATP2+) and one at which K+ is synergistic with Na+ and possibly antagonistic to Mg2+ (or MgATP2+). NH4+, Rb+, Cs+, but not Li+ can substitute for K+, but not for Na+ in reducing phosphorylation levels in the presence of Pb2+ and 3 mM MgCl2. The effects of these cations on native (Na+ + K+)-ATPase were similar. In the absence of Pb2+, K+ reduces the affinity for Na+ as measured by Na+-phosphorylation, but Na+ increases the affinity for K+ to the same extent at high and low [MgCl2], as measured by K+ dephosphorylation. Na+ potentiated by MgCl2 reduces the maximal K+ effect. The 2 loci for Na+-K+ interactions (antagonistic and synergistic) are consistent with these properties of the native enzyme and suggest Na+ regulates a balance between K+-MgCl2 interaction strengths at both sites. A model incorporating consecutive and simultaneous reactions of Na+ and K+ at different portions of the enzyme cycle appears best.


Accession: 005349226



Related references

Effects of lead ii ion and other divalent cations on ouabain binding to electrophorus electricus electroplax sodium potassium atpase. Molecular Pharmacology 15(1): 43-48, 1979

Irreversible zinc ion inhibition of sodium potassium atpase sodium phosphorylation and potassium p nitrophenyl phosphatase of electrophorus electricus electroplax. Journal of Neurochemistry 31(5): 1231-1238, 1978

Purification and properties of sodium potassium atpase from the rectal gland of squalus acanthias and the electric organ of electrophorus electricus and reconstitution of the sodium potassium pump from the purified enzyme. Semenza, G And E Carafoli (Ed ) Federation Of European Biochemical Societies Symposium, No 42 Biochemistry Of Membrane Transport Zurich, Switzerland, July 18-23, 1976 Xix+669p Illus Springer-Verlag: Berlin, West Germany; New York, N Y , Usa Isbn 3-540-08082-1; Isbn 0-387-08082-1 374-388, 1977

Characteristics of lead ion stimulated phosphorylation of electrophorus electricus electroplax sodium potassium atpase and inhibition of atp adp exchange. Journal of Biological Chemistry 253(20): 7207-7211, 1978

Detergent inactivation of sodium potassium atpase of the electric eel electrophorus electricus. Biochemistry 18(23): 5043-5050, 1979

Electrophorus electricus (Na+ + K+)-ATPase. Evidence for simultaneous Na+ and K+ binding in the presence of Pb2+. Journal of Biological Chemistry 255(9): 3935-3943, 1980

Purification and characterization of sodium ion plus potassium ion stimulated atpase part 8 altered sodium ion to potassium ion transport ratio in vesicles reconstituted with purified sodium ion plus potassium ion stimulated atpase that has been selectively modified with trypsin in presence of sodium chloride. Biochimica et Biophysica Acta 555(3): 485-492, 1979

Effect of denervation on the sodium, potassium ATPase activity of Electrophorus electricus (L.) electrocyte. Comparative Biochemistry and Physiology B Comparative Biochemistry 103(3): 623-628, 1992

Inhibition by lead ion of electrophorus electroplax sodium potassium atpase and potassium p nitrophenyl phosphatase. Journal of Biological Chemistry 252(15): 5201-5205, 1977

The large subunit of sodium potassium atpase from the electroplax of electrophorus electricus is a glyco protein. Biochemical & Biophysical Research Communications 90(2): 488-490, 1979