Binding of retinoids and β-carotene to β-lactoglobulin. Influence of protein modifications

• Published in: Biochimica et biophysica acta Vol. 1079; no. 3; pp. 316 - 320
• Main Authors: Dufour, Eric, Haertlé, Tomasz
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 20.09.1991; Elsevier
• Subjects: Analytical, structural and metabolic biochemistry; beta -carotene; Binding and carrier proteins; Biological and medical sciences; Carotenoids - metabolism; Fundamental and applied biological sciences. Psychology; Kinetics; Lactoglobulins - metabolism; Life Sciences; Ligand binding; Modification; Protein Binding; Proteins; retinoic acid; Retinoid; Retinoids - metabolism; retinol; retinyl acetate; Spectrometry, Fluorescence; Tretinoin - metabolism; Vitamin A - analogs & derivatives; Vitamin A - metabolism; ß-Carotene; ß-Lactoglobulin; Modification; Ligand binding; N-ethyllysyl-BLG; ß-Carotene; Retinoid; ß-Lactoglobulin; MetBLG; BLG; Lactoglobulins; Carotene; Dissociation constant; Retinoids; Carrier protein; Fluorescence spectrometry
• ISSN: 0167-4838; 0006-3002; 1879-2588
• DOI: 10.1016/0167-4838(91)90075-B

The binding of retinol, retinyl acetate, retinoic acid and ß-carotene to native, esterified and alkylated ß-lactoglobulin was followed by quenching of tryptophan fluorescence. Three studied retinoids bind to native or modified ß-lactoglobulin in 1 : 1 molar ratios, with apparent dissociation constants in the range of 10 −8 M. The maximum tryptophan fluorescence quenching of unmodified ß-lactoglobulin by ß-carotene is observed at the ligand/protein ratio of 1 : 2. Esterification and alkylation of ß-lactoglobulin shift the ratio of ß-carotene/protein to 1 : 1. In all the cases, except for retinoic acid binding to N-ethyllysyl-BLG, the performed chemical modifications of ß-lactoglobulin enhance protein binding affinity. Measured apparent dissociation constants of ß-carotene complexes with native and modified ß-lactoglobulin are an order of magnitude lower from binding constants of other studied retinoids.