title: Membrane topology of insulin receptors reconstituted into lipid vesicles.
abstract: Insulin receptors were incorporated into liposomes by two different procedures, one using dialysis and one using detergent removal by Bio-Beads. Receptor incorporation was analyzed by gradient centrifugation and electron microscopy. Reconstituted receptors projected up to 12 nm above the membrane and exhibited a T-shaped structure compatible with that previously described for the solubilized receptor. Insulin binding and autophosphorylation experiments indicated that approx. 50% of the receptors were incorporated right-side out. Such random orientation was confirmed by immunogold labeling of the alpha- and the beta-subunit of the receptor. Immunogold labeling of the C-terminus of the beta-subunit indicates that it resides about 6 nm off the membrane, while two alpha-subunit epitopes were labeled at about twice this distance, confirming that the alpha-subunit is harbored in the cross-bar of the T-structure.
authors.affiliation: Department of Medical Anatomy, Panum Institute, University of Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Tranum-Jensen
authors.forename: K
authors.initials: K
authors.lastname: Christiansen
authors.forename: J
authors.initials: J
authors.lastname: Carlsen
authors.forename: G
authors.initials: G
authors.lastname: Brenzel
authors.forename: J
authors.initials: J
authors.lastname: Vinten
mesh_terms: D006801:Humans; D007328:Insulin / Q000378:metabolism; D008081:Liposomes; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D008954:Models, Biological; D011972:Receptor, Insulin / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D007328:Insulin; D008081:Liposomes; D008567:Membranes, Artificial; D011972:Receptor, Insulin