[Calmodulin-dependent regulation of Ca,Mg-ATPase activity in plasma membranes of the swine myometrium].
Highly purified plasma membrane (PM) preparations of pig myometrium were found to contain 0.91 +/- 0.22 microgram calmodulin per mg of PM protein. Treatment of membranes with 1 mM EGTA in the presence of 0.2 M NaCl causes the diminution of the calmodulin content down to 3% of the original level. The activity of Ca, Mg-ATPase is thereby decreased by 40%. Exogenous calmodulin restores the enzyme activity up to 1.94 +/- +/- 0.30 mumol Pi/mg protein/hour. The maximal activation of Ca, Mg-ATPase is observed with 10(-7) M calmodulin. Calmodulin increases the total ATPase activity of myometrium PM without affecting the Mg-ATPase activity. Trifluoroperazine (20 microM) diminishes the activating effect of exogenous calmodulin on Ca, Mg-ATPase. Calmodulin stimulates Ca, Mg-ATPase at low concentrations of Ca2+(10(-8)-10(-6) M) by decreasing Km for Ca2+ from 0.4.10(-6) M to 2.10(-8) M as well as by increasing Vmax--from 0,8 to 1.42 mumol Pl/mg protein/hour. It is supposed that the activating effect of calmodulin on Ca, Mg-ATPase is based on electrostatic interactions of Ca2+-free calmodulin with the enzyme.
Kondratiuk
T P
TP
Prishchepa
L A
LA
Kurskiĭ
M D
MD
Osipenko
A A
AA
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002147:Calmodulin / Q000502:physiology*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation; D005260:Female; D007700:Kinetics; D009215:Myometrium / Q000201:enzymology*; D013552:Swine
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases
Kal'modulinzavisimaia reguliatsiia aktivnosti Ca,Mg-ATPazy plazmaticheskikh membran miometriia svin'i.