title: A monoclonal antibody to the calmodulin-binding (Ca2+ + Mg2+)-dependent ATPase from pig stomach smooth muscle inhibits plasmalemmal (Ca2+ + Mg2+)-dependent ATPase activity.
abstract: A monoclonal antibody (2B3) directed against the calmodulin-binding (Ca2+ + Mg2+)-dependent ATPase from pig stomach smooth muscle was prepared. This antibody reacts with a 130,000-Mr protein that co-migrates on SDS/polyacrylamide-gel electrophoresis with the calmodulin-binding (Ca2+ + Mg2+)-ATPase purified from smooth muscle by calmodulin affinity chromatography. The antibody causes partial inhibition of the (Ca2+ + Mg2+)-ATPase activity in plasma membranes from pig stomach smooth muscle, in pig erythrocytes and human erythrocytes. It appears to be directed against a specific functionally important site of the plasmalemmal Ca2+-transport ATPase and acts as a competitive inhibitor of ATP binding. Binding of the antibody does not change the Km of the ATPase for Ca2+ and its inhibitory effect is not altered by the presence of calmodulin. No inhibition of (Ca2+ + Mg2+)-ATPase activity or of the oxalate-stimulated Ca2+ uptake was observed in a pig smooth-muscle vesicle preparation enriched in endoplasmic reticulum. These results confirm the existence in smooth muscle of two different types of Ca2+-transport ATPase: a calmodulin-binding (Ca2+ + Mg2+)-ATPase located in the plasma membrane and a second one confined to the endoplasmic reticulum.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000302:isolation & purification; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000302:isolation & purification; D002147:Calmodulin / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D007163:Immunosorbent Techniques; D009130:Muscle, Smooth / Q000201:enzymology*; D013270:Stomach / Q000201:enzymology; D013552:Swine
chemical_list: D000911:Antibodies, Monoclonal; D002147:Calmodulin; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium