Effects of phospholipids on the function of (Ca2(+)-Mg2+)-ATPase.
The ATPase activity for the (Ca2(+)-Mg2+)-ATPase purified from rabbit skeletal muscle sarcoplasmic reticulum is lower when reconstituted into bilayers of dimyristoleoylphosphatidylcholine [(C14:1)PC] than when it is reconstituted into dioleoylphosphatidylcholine [(C18:1)PC]. The rate of formation of phosphoenzyme on addition of ATP is slower for (C14:1)PC-ATPase than for the native ATPase or (C18:1)PC-ATPase. The reduction in rate of phosphoenzyme formation is attributed to a reduction in the rate of a conformational change on the ATPase following binding of ATP but before phosphorylation. The level of phosphoenzyme formed from Pi is also less for (C14:1)PC-ATPase than for (C18:1)PC-ATPase. At steady state at pH 6.0 in the presence of ATP Ca2+ is released from (C18:1)PC-ATPase into the medium, but not from (C14:1)PC-ATPase. These effects of (C14:1)PC on the ATPase are reversed by addition of androstenol to a 1:1 molar ratio with (C14:1)PC. The results are interpreted in terms of a kinetic model for the ATPase.
Michelangeli
F
F
Department of Biochemistry, University of Southampton, U.K.
Grimes
E A
EA
East
J M
JM
Lee
A G
AG
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010743:Phospholipids / Q000502:physiology*; D010766:Phosphorylation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D013329:Structure-Activity Relationship
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010743:Phospholipids; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium