Binding of benzo(a)pyrene, ellipticine, and cis-parinaric acid to beta-lactoglobulin: influence of protein modifications.
The binding of benzo(a)pyrene, ellipticine, and cis-parinaric acid to native, esterified, and alkylated beta-lactoglobulin was followed by enhancement of the ligand fluorescence. Three studied ligands bind to native or modified beta-lactoglobulin in apparent molar ratios varying between 1/8 and 2/1, with apparent dissociation constants in the range of 10(-8) M for ligand/beta-lactoglobulin complexes. The studied, chemically modified beta-lactoglobulin derivatives display higher binding affinities for all studied ligands, cis-parinaric acid excluded. The reductive alkylation of epsilon-NH2 lysyl residues of beta-lactoglobulin increases the apparent molar ratios of benzo(a)pyrene and cis-parinaric acid, and decreases it for ellipticine. The esterified and native beta-lactoglobulin complexed to the investigated ligands display similar stoichiometries. Dynamic light scattering study of ligand-beta-lactoglobulin complexes in solution shows the formation of aggregates: the apparent hydrodynamic radius value of beta-lactoglobulin dimer (3.4 nm) reaches 49, 46, and 74 nm upon addition and binding of benzo(a)pyrene, ellipticine, and cis-parinaric acid, respectively.
Dufour
E
E
LEIMA-INRA, BP 527, Nantes, France.
Roger
P
P
Haertlé
T
T
D000478:Alkylation; D001564:Benzo(a)pyrene / Q000378:metabolism*; D004611:Ellipticines / Q000378:metabolism*; D004951:Esterification; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007782:Lactoglobulins / Q000378:metabolism*; D008027:Light; D008745:Methylation; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence
D004611:Ellipticines; D005231:Fatty Acids, Unsaturated; D007782:Lactoglobulins; C034192:ellipticine; D001564:Benzo(a)pyrene; C013641:parinaric acid