title: The topological orientation of N,N'-diacetylchitobiosylpyrophosphoryldolichol in artificial and natural membranes.
abstract: Purified N,N'-diacetylchitobiosylpyrophosphoryldolichol (chitobiosyl-lipid) in the presence of detergent was shown to act as a substrate for the soluble enzyme galactosyltransferase. The nature of this transfer reaction and the galactose-containing trisaccharide-lipid product have been partially characterized. Using galactosyltransferase as a probe, the topolical arrangement of chitobiosyl-lipid in both artificial and natural membranes has been examined. When incorporated into unilamellar liposomes made from phosphatidylcholine, the disaccharide residue of chitogiosyl-lipid adopts a random transbilayer orientation. Furthermore, no significant mobility in the transverse plane of the membrane (i.e. flip-flop) is detectable. Using both sealed total microsomes or isolated rough microsomes from hen oviduct, the topology of chitobiosyl-lipid after its biosynthesis in the membrane has been determined. The results suggest that, once formed, chitobiosyl-lipid is a relatively static component of the membrane and is oriented with its disaccharide residue facing the lumen of the endoplasmic reticulum.
mesh_terms: D000117:Acetylglucosamine / Q000031:analogs & derivatives / Q000032:analysis; D000818:Animals; D002645:Chickens; D005260:Female; D005700:Galactosyltransferases / Q000378:metabolism; D007425:Intracellular Membranes / Q000648:ultrastructure; D007700:Kinetics; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids / Q000032:analysis*; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D008861:Microsomes / Q000648:ultrastructure; D010057:Oviducts / Q000032:analysis; D011104:Polyisoprenyl Phosphate Oligosaccharides / Q000032:analysis*; D011105:Polyisoprenyl Phosphate Sugars / Q000032:analysis*; D011487:Protein Conformation; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D008567:Membranes, Artificial; D011104:Polyisoprenyl Phosphate Oligosaccharides; D011105:Polyisoprenyl Phosphate Sugars; D014537:Uridine Diphosphate N-Acetylglucosamine; C007292:P'-di-N-acetylchitobiosyl-P(2)-dolichylpyrophosphate; D005700:Galactosyltransferases; D000117:Acetylglucosamine