title: Interactions of β-lactoglobulin variants A and B with Vitamin A. Competitive binding of retinoids and carotenoids.
abstract: β-Lactoglobulin (β-Lg) is the major whey protein of bovine milk present at a concentration of 2-3 g L(-1). Its biological role is still not well-known. However, many studies have suggested that β-Lg may play either nutritional or specific transporter role. The high affinity of β-Lg for retinol and other retinoids was reported. The results of interaction studies of β-Lg with carotenoids, that is, β-carotene, β-cryptoxanthin, and α-carotene, which display similar structures are reported in this study. The affinities of β-Lg for binding of retinoids and carotenoids were compared, providing more information about the binding site(s) of these molecules by β-Lg. Interactions were followed by the measurements of quenching of β-Lg tryptophan fluorescence and retinol fluorescence. The obtained results indicate that carotenoids are bound by β-Lg with high affinity of the order of 10(-8) M. Measurement of retinol competition with carotenoids for binding by β-Lg suggests that the binding of these two ligands occurs at two different sites of β-Lg.
authors.affiliation: UR 1268, INRA Biopolymères Interactions Assemblages-équipe Fonctions et Interactions des Protéines, rue de la Géraudière, B.P. 71627, 44316 Nantes Cedex 03, France.
authors.forename: Azza
authors.initials: A
authors.lastname: Mensi
authors.forename: Yvan
authors.initials: Y
authors.lastname: Choiset
authors.forename: Hanitra
authors.initials: H
authors.lastname: Rabesona
authors.forename: Thomas
authors.initials: T
authors.lastname: Haertlé
authors.forename: Patrick
authors.initials: P
authors.lastname: Borel
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Chobert
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002338:Carotenoids / Q000737:chemistry*; D065366:Cryptoxanthins; D057927:Hydrophobic and Hydrophilic Interactions; D007782:Lactoglobulins / Q000737:chemistry*; D008024:Ligands; D008894:Milk Proteins / Q000737:chemistry; D019308:Palmitic Acid / Q000737:chemistry; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D014801:Vitamin A / Q000737:chemistry*; D000067816:Whey Proteins; D024341:Xanthophylls / Q000737:chemistry*; D019207:beta Carotene / Q000737:chemistry*
chemical_list: D065366:Cryptoxanthins; D007782:Lactoglobulins; D008024:Ligands; D008894:Milk Proteins; D000067816:Whey Proteins; D024341:Xanthophylls; D019207:beta Carotene; D014801:Vitamin A; D019308:Palmitic Acid; D002338:Carotenoids; C041635:alpha-carotene