β‐Lactoglobulin binds retinol and protoporphyrin IX at two different binding sites

FEBS Letters

Haertlé, Tomasz²  Marden, Michael C.¹  Dufour, Eric² 

[1] INSERM U299, Hôpital de Bicêtre, 94275 Le Kremlin Bicêtre, France;LEIM A, Institut National de la Recherche Agronomique, BP 527, 44026 Nantes Cédex 03, France

关键词: β-Lactoglobulin;    Protoporphyrin IX;    Retinol;    Binding site;    BLG;    β-lactoglobulin;    PPIX;    protoporphyrin IX;   

DOI  :  10.1016/0014-5793(90)80850-I

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Measurement of tryptophan fluorescence quenching and the excitation energy transfer from tryptophanyl residues to the bound ligand indicates that β-lactoglobulin binds tightly to hemin and protoporphyrin IX in a ligand-to-protein stoichiometric ratio. The apparent dissociation constants of hemin-β-lactoglobulin and protoporphyrin IX-β-lactoglobulin complexes are 2.5 × 10⁻⁷ M and 4 × 10⁻⁷ M, respectively. The addition of β-lactoglobulin (final concentration = 10 μM, phosphate buffer 50 mM, pH 7.1) to the solution containing retinol and protoporphyrin IX triggers an energy transfer between β-lactoglobulin tryptophan and protoporphyrin IX as well as between retinol and protoporphyrin IX. The efficiency of energy transfer depends on the distance between the donor (retinol) and the acceptor (protoporphyrin IX). Using the Förster theory, a retinol-protoporphyrin IX distance of 25 Å was calculated. These results indicate that retinol and protoporphyrin IX are bound to the β-lactoglobulin monomer at two different sites.

【 授权许可】

Unknown