Characterization of the vitamin E-binding properties of human plasma afamin

Biochemistry. 2002 Dec 10;41(49):14532-8. doi: 10.1021/bi026513v.


Human plasma afamin, the fourth member of the albumin gene family, is shown to be a specific binding protein for vitamin E. A radio ligand-binding assay followed by Scatchard and Hill analysis are used to show that afamin has a binding affinity for both alpha-tocopherol and gamma-tocopherol, two of the most important forms of vitamin E, in vitro. The binding-dissociation constant was determined to be 18 microM, indicating that afamin plays a role as vitamin E carrier in body fluids such as human plasma and follicular fluid under physiological conditions. Additionally, we demonstrate that afamin has multiple binding sites for both alpha- and gamma-tocopherol. Due to the large binding capacity of afamin for vitamin E, it might take over the role of vitamin E transport in body fluids under conditions where the lipoprotein system is not sufficient for vitamin E transport. To confirm the experimental results, we performed homology modeling and docking calculations on the predicted tertiary structure, which showed coincidence between calculated and in vitro results.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Binding Sites
  • Carrier Proteins / blood
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism
  • Computer Simulation
  • Glycoproteins*
  • Humans
  • Kinetics
  • Models, Molecular
  • Protein Binding
  • Sequence Homology, Amino Acid
  • Serum Albumin / chemistry*
  • Serum Albumin / metabolism
  • Serum Albumin, Human
  • Thermodynamics
  • Vitamin E / metabolism*


  • AFM protein, human
  • Carrier Proteins
  • Glycoproteins
  • Serum Albumin
  • alpha-tocopherol transfer protein
  • Vitamin E
  • Serum Albumin, Human