A high-affinity, calmodulin-sensitive (Ca2+ + Mg2+)-ATPase and associated calcium-transport pump in the Ehrlich ascites tumor cell plasma membrane. 1983

N B Klaven, and H A Pershadsingh, and G V Henius, and P C Laris, and J W Long, and J M McDonald

A unique cytoplast preparation from Ehrlich ascites tumor cells (G. V. Henius, P. C. Laris, and J. D. Woodburn (1979) Exp. Cell. Res. 121, 337-345), highly enriched in plasma membranes, was employed to characterize the high-affinity plasma membrane calcium-extrusion pump and its associated adenosine triphosphatase (ATPase). An ATP-dependent calcium-transport system which had a high affinity for free calcium (K0.5 = 0.040 +/- 0.005 microM) was identified. Two different calcium-stimulated ATPase activities were detected. One had a low (K0.5 = 136 +/- 10 microM) and the other a high (K0.5 = 0.103 +/- 0.077 microM) affinity for free calcium. The high-affinity enzyme appeared to represent the ubiquitous high-affinity plasma membrane (Ca2+ + Mg2+)-ATPase (calcium-stimulated, magnesium-dependent ATPase) seen in normal cells. Both calcium transport and the (Ca2+ + Mg2+)-ATPase were significantly stimulated by the calcium-dependent regulatory protein calmodulin, especially when endogenous activator was removed by treatment with the calcium chelator ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid. Other similarities between calcium transport and the (Ca2+ + Mg2+)-ATPase included an insensitivity to ouabain (0.5 mM), lack of activation by potassium (20 mM), and a requirement for magnesium. These similar properties suggested that the (Ca2+ + Mg2+)-ATPase represents the enzymatic basis of the high-affinity calcium pump. The calcium pump/enzyme system was inhibited by orthovanadate at comparatively high concentrations (calcium transport: K0.5 congruent to 100 microM; (Ca2+ + Mg2+)-ATPase: K0.5 greater than 100 microM). Upon Hill analysis, the tumor cell (Ca2+ + Mg2+)-ATPase failed to exhibit cooperative activation by calcium which is characteristic of the analogous enzyme in the plasma membrane of normal cells.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002147 Calmodulin A heat-stable, low-molecular-weight activator protein found mainly in the brain and heart. The binding of calcium ions to this protein allows this protein to bind to cyclic nucleotide phosphodiesterases and to adenyl cyclase with subsequent activation. Thereby this protein modulates cyclic AMP and cyclic GMP levels. Calcium-Dependent Activator Protein,Calcium-Dependent Regulator,Bovine Activator Protein,Cyclic AMP-Phosphodiesterase Activator,Phosphodiesterase Activating Factor,Phosphodiesterase Activator Protein,Phosphodiesterase Protein Activator,Regulator, Calcium-Dependent,AMP-Phosphodiesterase Activator, Cyclic,Activating Factor, Phosphodiesterase,Activator Protein, Bovine,Activator Protein, Calcium-Dependent,Activator Protein, Phosphodiesterase,Activator, Cyclic AMP-Phosphodiesterase,Activator, Phosphodiesterase Protein,Calcium Dependent Activator Protein,Calcium Dependent Regulator,Cyclic AMP Phosphodiesterase Activator,Factor, Phosphodiesterase Activating,Protein Activator, Phosphodiesterase,Protein, Bovine Activator,Protein, Calcium-Dependent Activator,Protein, Phosphodiesterase Activator,Regulator, Calcium Dependent
D002286 Carcinoma, Ehrlich Tumor A transplantable, poorly differentiated malignant tumor which appeared originally as a spontaneous breast carcinoma in a mouse. It grows in both solid and ascitic forms. Ehrlich Ascites Tumor,Ascites Tumor, Ehrlich,Ehrlich Tumor Carcinoma,Tumor, Ehrlich Ascites
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002614 Chelating Agents Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS. Chelating Agent,Chelator,Complexons,Metal Antagonists,Chelators,Metal Chelating Agents,Agent, Chelating,Agents, Chelating,Agents, Metal Chelating,Antagonists, Metal,Chelating Agents, Metal
D000252 Calcium-Transporting ATPases Cation-transporting proteins that utilize the energy of ATP hydrolysis for the transport of CALCIUM. They differ from CALCIUM CHANNELS which allow calcium to pass through a membrane without the use of energy. ATPase, Calcium,Adenosinetriphosphatase, Calcium,Ca(2+)-Transporting ATPase,Calcium ATPase,Calcium Adenosinetriphosphatase,Adenosine Triphosphatase, Calcium,Ca2+ ATPase,Calcium-ATPase,ATPase, Ca2+,ATPases, Calcium-Transporting,Calcium Adenosine Triphosphatase,Calcium Transporting ATPases,Triphosphatase, Calcium Adenosine
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
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
D001693 Biological Transport, Active The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy. Active Transport,Uphill Transport,Active Biological Transport,Biologic Transport, Active,Transport, Active Biological,Active Biologic Transport,Transport, Active,Transport, Active Biologic,Transport, Uphill

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