title: Determination of the molecular mass of the native beta-cell sulfonylurea receptor.
abstract: In the present study we have determined the molecular mass of the beta-cell sulfonylurea receptor in its native form by two different experimental approaches; gel filtration chromatography and radiation inactivation analysis. We first confirmed that the denatured photolabelled MIN6 beta-cell receptor had a molecular size of 141 +/- 2 kDa (mean +/- S.E., n = 8). Under non-denaturing conditions, using gel filtration chromatography, apparent molecular masses of 166 +/- 1 kDa (mean +/- S.E., n = 3) and 182 +/- 5 kDa (mean +/- S.E., n = 4) were determined for the photoaffinity-labelled and unlabelled sulfonylurea receptor, respectively. We conclude that in the solubilized state the receptor exists as a monomer. Radiation inactivation analysis indicated that the receptor has a target size of 250 +/- 30 kDa (mean +/- S.E., n = 7). This value for the molecular mass is larger than that obtained from SDS-PAGE following photolabelling of the receptor (141 kDa) suggesting that the beta-cell sulfonylurea receptor is composed of more than one subunit in the native membrane.
authors.affiliation: Nuffield Department of Clinical Biochemistry, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Skeer
authors.forename: P
authors.initials: P
authors.lastname: Dégano
authors.forename: B
authors.initials: B
authors.lastname: Coles
authors.forename: M
authors.initials: M
authors.lastname: Potier
authors.forename: F M
authors.initials: FM
authors.lastname: Ashcroft
authors.forename: S J
authors.initials: SJ
authors.lastname: Ashcroft
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000345:Affinity Labels; D002462:Cell Membrane / Q000737:chemistry; D002478:Cells, Cultured; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D007515:Islets of Langerhans / Q000737:chemistry*; D008970:Molecular Weight; D015221:Potassium Channels / Q000737:chemistry* / Q000528:radiation effects; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug / Q000737:chemistry* / Q000528:radiation effects; D064233:Sulfonylurea Receptors
chemical_list: D018528:ATP-Binding Cassette Transporters; D000345:Affinity Labels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors