Inhibitory antibodies to plasmalemmal Ca2+-transporting ATPases. Their use in subcellular localization of (Ca2+ + Mg2+)-dependent ATPase activity in smooth muscle.
Antibodies directed against the purified calmodulin-binding (Ca2+ + Mg2+)-ATPase [(Ca2+ + Mg2+)-dependent ATPase] from pig erythrocytes and from smooth muscle of pig stomach (antral part) were raised in rabbits. Both the IgGs against the erythrocyte (Ca2+ + Mg2+)-ATPase and against the smooth-muscle (Ca2+ + Mg2+)-ATPase inhibited the activity of the purified calmodulin-binding (Ca2+ + Mg2+)-ATPase from smooth muscle. Up to 85% of the total (Ca2+ + Mg2+)-ATPase activity in a preparation of KCl-extracted smooth-muscle membranes was inhibited by these antibodies. The (Ca2+ + Mg2+)-ATPase activity and the Ca2+ uptake in a plasma-membrane-enriched fraction from this smooth muscle were inhibited to the same extent, whereas in an endoplasmic-reticulum-enriched membrane fraction the (Ca2+ + Mg2+)-ATPase activity was inhibited by only 25% and no effect was observed on the oxalate-stimulated Ca2+ uptake. This supports the hypothesis that, in pig stomach smooth muscle, two separate types of Ca2+-transport ATPase exist: a calmodulin-binding ATPase located in the plasma membrane and a calmodulin-independent one present in the endoplasmic reticulum. The antibodies did not affect the stimulation of the (Ca2+ + Mg2+)-ATPase activity by calmodulin.
Verbist
J
J
Wuytack
F
F
Raeymaekers
L
L
Casteels
R
R
D000818:Animals; D000906:Antibodies / Q000276:immunology; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000276:immunology* / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D007074:Immunoglobulin G / Q000276:immunology; D009130:Muscle, Smooth / Q000201:enzymology* / Q000276:immunology; D013347:Subcellular Fractions / Q000201:enzymology; D013552:Swine
D000906:Antibodies; D007074:Immunoglobulin G; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium