title: Cooperative lipid activation of (Na+ + K+)-ATPASE as a consequence of non-cooperative lipid-protein interactions.
abstract: Lipid activation data for (Na+ + K+)-ATPase (Ottolenghi, P. (1979) Eur. J. Biochem. 99, 113-131) have been subjected to a regression and fitting analysis based on a recent kinetic model (Sandermann, H. (1982) Eur. J. Biochem, 127, 123-128). The observed kinetic cooperativity could be generated from strictly non-cooperative binding events involving the known number of 30 boundary lipid-binding sites per ATPase monomer. Apparent lipid dissociation equilibrium constants of between 0.3 and 5 microM were obtained, enzyme activity being associated only with the fully lipid-substituted enzyme and enzyme-lipid complexes with less than six unoccupied lipid-binding sites. The enzyme appeared to operate close to a maximum of cooperativity.
mesh_terms: D000818:Animals; D001665:Binding Sites; D004284:Dogfish; D004789:Enzyme Activation; D007700:Kinetics; D008563:Membrane Lipids / Q000502:physiology*; D010713:Phosphatidylcholines / Q000494:pharmacology*; D010714:Phosphatidylethanolamines / Q000494:pharmacology*; D011485:Protein Binding; D012007:Rectum / Q000201:enzymology*; D012627:Sebaceous Glands / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C020888:1,2-dielaidoylphosphatidylethanolamine; D000254:Sodium-Potassium-Exchanging ATPase; C017251:1,2-oleoylphosphatidylcholine