Two populations of phospholipids exist in sarcoplasmic reticulum and in recombined membranes containing Ca-ATPase.
Phosphorus nuclear magnetic resonance spectra of sarcoplasmic reticulum membranes from rabbit muscle and of recombined membranes containing the calcium-dependent adenosinetriphosphatase (Ca-ATPase) of sarcoplasmic reticulum reveal two distinguishable, overlapping resonances. One resonance resembles a normal phospholipid bilayer resonance, and the other is much broader. The broader component is not seen in protein-free phospholipid vesicles. In recombined membranes of the Ca-ATPase, the intensity found in the broad component was proportional to the concentration of protein in the vesicles. The two-component spectra are interpreted to arise from at least two different domains of phospholipids, one of which is motionally restricted by the Ca-ATPase. Phospholipids exchange between these two domains at a rate less than 10(3) s-1. A model for protein-lipid interactions in membranes containing the Ca-ATPase is proposed in which some of the phospholipid head groups of the membrane interact directly with the protein.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008563:Membrane Lipids / Q000032:analysis*; D008565:Membrane Proteins / Q000378:metabolism; D010743:Phospholipids / Q000032:analysis*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000032:analysis*
D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D000252:Calcium-Transporting ATPases