Differences in heat stability and ligand binding among β-lactoglobulin genetic variants A, B and C using (1)H NMR and fluorescence quenching.

The structure of β-lactoglobulin (β-LG) is well characterized, but the exact location of binding sites for retinol and (-)-epigallocatechingallate (EGCG) is still a subject of controversy. Here we report that the genetic β-LG variants A, B and C have different numbers of binding sites for retinol (almost completely incorporated into the calyx), as well as for EGCG (exclusively bound on the surface), and β-LG A with the most binding sites for EGCG, which include Tyr(20), Phe(151) and His(59). Upon heat related unfolding, new unspecific binding sites emerge, which are comparable in number and affinity for retinol and for EGCG, and in the three genetic variants A, B and C. The findings of our study provide new insights into the use of β-LG as nanotransporter.