Membrane fluidity is not an important physiological regulator of the (Ca2+-Mg2+)-dependent ATPase of sarcoplasmic reticulum.
The (Ca2+-Mg2+)-ATPase from sarcoplasmic reticulum has been reconstituted into phospholipid bilayers of different fatty acyl chain length and degree of unsaturation, and ATPase activity was found to vary about 10-fold. Order parameters for bilayers of these lipids measured using the ESR probe 5-doxylstearic acid varied from 0.5 to 0.6 at 37 degrees C. There was no correlation between phospholipid order parameter and ATPase activity, and we conclude that phospholipid structure is a more important determinant of protein activity than is membrane fluidity.
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008051:Lipid Bilayers; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000502:physiology; D010743:Phospholipids / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
D008051:Lipid Bilayers; D008563:Membrane Lipids; D010743:Phospholipids; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases