Transmembrane Ca2+ gradient-mediated modulation of sarcoplasmic reticulum Ca(2+)-ATPase.
Ca(2+)-ATPase from skeletal muscle sarcoplasmic reticulum was reconstituted into liposomes with (100-1000 fold) or without transmembrane Ca2+ gradient. The highest enzyme activity and Ca2+ uptake were observed in the vesicles without transmembrane Ca2+ gradient. If there existed transmembrane Ca2+ gradient, no matter what the direction was, a lower activity would appear. Dissipation of transmembrane Ca2+ gradient by A23187 could lead to a change in enzyme activity of incorporated Ca(2+)-ATPase. A concomitant change of lipid fluidity of proteoliposomes with that of enzyme activity and Ca2+ uptake was observed. The inhibition of Ca(2+)-ATPase by the transmembrane Ca2+ gradient could be observed in the PC-PE vesicles, but not in the PS-PE or PG-PE proteoliposomes.
Tu
Y P
YP
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, China.
Yang
F Y
FY
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes / Q000378:metabolism; D009132:Muscles / Q000201:enzymology; D010743:Phospholipids / Q000494:pharmacology; D011510:Proteolipids / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
D008081:Liposomes; D010743:Phospholipids; D011510:Proteolipids; C020485:proteoliposomes; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium