Direct photoaffinity labeling of the putative sulfonylurea receptor in rat β‐cell tumor membranes by [3H]glibenclamide

Abstract The oral antidiabetic sulfonylurea [ 3 H]glibenclamide specifically binds to plasma membranes from a rat β-cell tumor indicating a receptor for sulfonylureas in these membranes. Irradiation of [ 3 H]glibenclamide at 254 or 300 nm in the presence of albumin resulted in covalent labeling of the albumin molecule. Direct photoaffinity labeling of β-cell membranes with [ 3 H]glibenclamide resulted in the covalent modification of two membrane polypeptides with apparent molecular masses 140 and 33 kDa. The extent of labeling of the 140 kDa polypeptide was specifically decreased by sulfonylureas. This suggests that a membrane polypeptide of 140 kDa is a component of the sulfonylurea receptor in the β-cell membrane.