Binding of retinoids and beta-carotene to beta-lactoglobulin. Influence of protein modifications.
The binding of retinol, retinyl acetate, retinoic acid and beta-carotene to native, esterified and alkylated beta-lactoglobulin was followed by quenching of tryptophan fluorescence. Three studied retinoids bind to native or modified beta-lactoglobulin in 1:1 molar ratios, with apparent dissociation constants in the range of 10(-8) M. The maximum tryptophan fluorescence quenching of unmodified beta-lactoglobulin by beta-carotene is observed at the ligand/protein ratio of 1:2. Esterification and alkylation of beta-lactoglobulin shift the ratio of beta-carotene/protein to 1:1. In all the cases, except for retinoic acid binding to N-ethyllysyl-BLG, the performed chemical modifications of beta-lactoglobulin enhance protein binding affinity. Measured apparent dissociation constants of beta-carotene complexes with native and modified beta-lactoglobulin are an order of magnitude lower from binding constants of other studied retinoids.
Dufour
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E
L.E.I.M.A., Institut National de la Recherche Agronomique, Nantes, France.
Haertlé
T
T
D002338:Carotenoids / Q000378:metabolism*; D004224:Diterpenes; D007700:Kinetics; D007782:Lactoglobulins / Q000378:metabolism*; D011485:Protein Binding; D012176:Retinoids / Q000378:metabolism*; D000084562:Retinyl Esters; D013050:Spectrometry, Fluorescence; D014212:Tretinoin / Q000378:metabolism; D014801:Vitamin A / Q000031:analogs & derivatives / Q000378:metabolism; D019207:beta Carotene
D004224:Diterpenes; D007782:Lactoglobulins; D012176:Retinoids; D000084562:Retinyl Esters; D019207:beta Carotene; D014801:Vitamin A; D002338:Carotenoids; C009166:retinol acetate; D014212:Tretinoin