title: The structure of beta-lactoglobulin and its similarity to plasma retinol-binding protein.
abstract: Since its first isolation, bovine beta-lactoglobulin (BLG) has been an enigma: although it is abundant in the whey fraction of milk, its function is still not clear. The results of the many physicochemical studies on the protein need a structural interpretation. We report here the structure of the orthorhombic crystal form of cow BLG at pH 7.6, at a resolution of 2.8 A. It has an unusual protein fold, composed of two slabs of antiparallel beta-sheet, which shows a remarkable similarity to plasma retinol-binding protein. A possible binding site for retinol in BLG has been identified by model-building. This suggests a role for BLG in vitamin A transport and we have discovered specific receptors for the BLG-retinol complex in the intestine of neonate calves.
mesh_terms: D000818:Animals; D002417:Cattle; D007782:Lactoglobulins; D008958:Models, Molecular; D011487:Protein Conformation; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma
chemical_list: D007782:Lactoglobulins; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma