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/sup 31/P NMR studies of oriented multilayers formed from isolated sarcoplasmic reticulum and reconstituted sarcoplasmic reticulum: evidence that boundary-layer phospholipid is not immobilized

Conference ·
OSTI ID:6299728

The major protein constituent of the sarcoplasmic reticulum is the calcium-pump protein which has been dissociated from the sarcoplasmic reticulum membrane and reconstituted to form functional membrane vesicles. The angular dependence of the /sup 31/P NMR signal from oriented sarcoplasmic reticulum membranes was obtained. Similar spectra were obtained from oriented reconstituted sarcoplasmic reticulum membranes with lipid-to-protein ratios ranging from 42:1 to 110:1 and from oriented bilayer membranes formed from sarcoplasmic reticulum phospholipids. Two conclusions were drawn from the /sup 31/P NMR spectra about the motion of the phospholipid molecules that contribute to the observed spectra. First, the phosphate group and the two adjacent methylene groups are able to rapidly rotate around the normal to the plane of the membrane. Second, the restricted internal motion of the phosphate group and the glycerol CH/sub 2/OP group is very similar to that found in liposomes formed from sarcoplasmic reticulum phospholipids. Calibration experiments showed that all of the phospholipid molecules in the membranes can be accounted for in the observed spectra. Thus, essentially all the phospholipid molecules in the sarcoplasmic reticulum and the reconstituted sarcoplasmic reticulum membranes have the same motion in the polar headgroup region as found in model bilayer membranes. Since a large fraction of the phospholipid molecules are immediately surrounding the calcium-pump protein it was concluded that the calcium-pump protein does not perturb the motion of these boundary-layer lipids. (ERB)

Research Organization:
Brookhaven National Lab., Upton, NY (USA); Pennsylvania Univ., Philadelphia (USA); Vanderbilt Univ., Nashville, TN (USA). Dept. of Molecular Biology
DOE Contract Number:
AC02-76CH00016
OSTI ID:
6299728
Report Number(s):
BNL-29466; CONF-811009-1; ON: DE81021388
Country of Publication:
United States
Language:
English