Stimulation of the catalytic cycle of the Ca2+ pump of porcine plasma-membranes by negatively charged phospholipids.
The (Ca(2+)+Mg2+)-ATPase of the plasma membrane is activated by negatively charged phospholipids. The mechanism of this activation was investigated by studying the effect of negatively charged phospholipids on the steady-state phosphointermediate level and on the p-nitrophenylphosphatase activity. Both parameters were differentially affected by different acidic phospholipids. The level of phosphoprotein intermediate was not affected by phosphatidylserine (20% of total phospholipid), but it was increased by 60% by phosphatidylinositol 4-phosphate. Phosphatidylserine increased the p-nitrophenylphosphatase activity, whereas phosphatidylinositol 4-phosphate had no significant effect. It is suggested that phosphatidylinositol 4-phosphate mainly affects a reaction step which leads to accelerated formation of the phosphointermediate, whereas the action of phosphatidylserine would affect two reaction steps, one upstream and one downstream of the phosphointermediate.
Lehotsky
J
J
Laboratory of Physiology, K.U. Leuven, Belgium.
Raeymaekers
L
L
Missiaen
L
L
Wuytack
F
F
De Smedt
H
H
Casteels
R
R
D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002384:Catalysis; D004563:Electrochemistry; D004910:Erythrocyte Membrane / Q000201:enzymology / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry / Q000494:pharmacology*; D010766:Phosphorylation; D013552:Swine
D010743:Phospholipids; D009597:4-Nitrophenylphosphatase; D000252:Calcium-Transporting ATPases