Interaction of Lanthanide Ions With the Sarcoplasmic Reticulum (Ca2++Mg2+)-ATPase

The effect and mechanism of action of lanthanide ions on sarcoplasmic reticulum (SR) (Ca2++Mg2+)-ATPase activity are investigated. Low concentrations of Gd3+ stimulate the SR ATPase activity and the activity is inhibited with the increasing of the concentrations of Gd3+. Gd3+ inhibits the purified ATPase activity. When the purified ATPase is reconstituted with phosphatidic acid (PA) or cardiolipin (CL), low concentrations of Gd3+ activate its activity, whereas the activity will be inhibited if the enzyme is reconstituted with phosphatidylcholine (PC), phosphatidylserine (PS) and the mixture of phosphatidylcholine and phosphatidylethanolamine (PC/PE). Furthermore, different actions of Tb3+ on Ca2+-binding sites of the SR and purified ATPase have been observed.