Biomaterial Database

Characteristics of antibody inhibition of rat kidney (Na+ -K+)-ATPase. 1978

H Koepsell

Antibodies which were raised against highly purified membrane-bound (Na+ -K+)-ATPase from the outer medulla of rat kidneys inhibit the (Na+-K+)-ATPase activity up to 95%. The antibody inhibition is reversible. The time course of enzyme inhibition and reactivation is biphasic in semilogarithmic plots. In the purified membrane-bound (Na+-K+)-ATPase negative cooperativity was observed (a) for the ATP dependence of the (Na+ -K+)-ATPase activity (n = 0.86), (b) for the ATP binding to the enzyme (n = 0.58), and (c) for the ouabain inhibition of the (Na+ -K+)-ATPase activity (n = 0.77). By measuring the Na+ dependence of the (Na+ -K+)-ATPase reaction, a positive homotropic cooperativity (n = 1.67) was found. As reactivation of the antibody-inhibited enzyme proceeds very slowly (t0.5 = 5.2 hr), it was possible to measure characteristics of the antibody-(Na+ -K+)-ATPase complex: The antibodies exerted similar effects on the ATP dependence of the (Na+ -K+)-ATPase reaction and on the ATP binding of the enzyme. Vmax of the (Na+ -K+)-ATPase reaction and the number of ATP binding sites were reduced while K0.5 ATP for the (Na+ -K+)-ATPase activity and for the ATP binding were increased by the antibodies. The Hill coefficients for the ATP binding and for the ATP dependence of the enzyme activity were not significantly altered by the antibodies. The antibodies increased the K0.5 value for the Na+ stimulation of the (Na+ -K+)-ATPase activity, but they did not alter the homotropic interactions between the Na+-binding sites. The negative cooperativity which was observed for the ouabain inhibition of the (Na+ -K)-ATPase activity was abolished by the antibodies. The data are tentatively explained by the following model: The antibodies bind to the (Na+ -K+)-ATPase from the inner membrane side, reduce the ATP binding symmetrically at the ATP binding sites and reduce thereby also the (Na+ -K+)-ATPase activity of the enzyme. The antibodies may inhibit the ATP binding by a direct interaction or by means of a conformational change at the ATP binding sites. This may possibly also lead to the alteration of the Na+ dependence of the (Na+ -K+)-ATPase activity and to the observed alteration of the dose response to the ouabain inhibition.

UI	MeSH Term	Description	Entries
D007074	Immunoglobulin G	The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.	Gamma Globulin, 7S,IgG,IgG Antibody,Allerglobuline,IgG(T),IgG1,IgG2,IgG2A,IgG2B,IgG3,IgG4,Immunoglobulin GT,Polyglobin,7S Gamma Globulin,Antibody, IgG,GT, Immunoglobulin
D007668	Kidney	Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.	Kidneys
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D000254	Sodium-Potassium-Exchanging ATPase	An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.	ATPase, Sodium, Potassium,Adenosinetriphosphatase, Sodium, Potassium,Na(+)-K(+)-Exchanging ATPase,Na(+)-K(+)-Transporting ATPase,Potassium Pump,Sodium Pump,Sodium, Potassium ATPase,Sodium, Potassium Adenosinetriphosphatase,Sodium-Potassium Pump,Adenosine Triphosphatase, Sodium, Potassium,Na(+) K(+)-Transporting ATPase,Sodium, Potassium Adenosine Triphosphatase,ATPase Sodium, Potassium,ATPase, Sodium-Potassium-Exchanging,Adenosinetriphosphatase Sodium, Potassium,Pump, Potassium,Pump, Sodium,Pump, Sodium-Potassium,Sodium Potassium Exchanging ATPase,Sodium Potassium Pump
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D000906	Antibodies	Immunoglobulin molecules having a specific amino acid sequence by virtue of which they interact only with the ANTIGEN (or a very similar shape) that induced their synthesis in cells of the lymphoid series (especially PLASMA CELLS).
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining