α-Tocopherol binding to human serum albumin

Given the ability of human serum albumin (HSA) to bind hydrophobic ligands, the binding mode of α-tocopherol, the most representative member of the vitamin E family, is reported. α-Tocopherol binds to HSA with K $_{\rm d}^0$ = (7.0 ± 3.0) × 10-6 M (pH 7.2, 25.0°C). Competitive and allosteric modulation of α-tocopherol binding to full-length and truncated (Asp1-Glu382) HSA by endogenous and exogenous ligands suggests that it accommodates preferentially in the FA3-FA4 site. As HSA is taken up into cells, colocalizes with the α-tocopherol transfer protein, and contributes to ligand secretion via ABCA1, it might participate in the distribution of α-tocopherol between plasma, cells, and tissues.