The Molecular Basis of Vitamin E Retention: Structure of Human Alpha-Tocopherol Transfer ProteinMeier, R., Tomizaki, T., Schulze-Briese, C., Baumann, U., Stocker, A.
(2003) J Mol Biol 331: 725
- PubMed: 12899840
- DOI: https://doi.org/10.1016/s0022-2836(03)00724-1
- Primary Citation of Related Structures:
- PubMed Abstract:
Alpha-tocopherol transfer protein (alpha-TTP) is a liver protein responsible for the selective retention of alpha-tocopherol from dietary vitamin E, which is a mixture of alpha, beta, gamma, and delta-tocopherols and the corresponding tocotrienols. The alpha-TTP-mediated transfer of alpha-tocopherol into nascent VLDL is the major determinant of plasma alpha-tocopherol levels in humans. Mutations in the alpha-TTP gene have been detected in patients suffering from low plasma alpha-tocopherol and ataxia with isolated vitamin E deficiency (AVED). The crystal structure of alpha-TTP reveals two conformations. In its closed tocopherol-charged form, a mobile helical surface segment seals the hydrophobic binding pocket. In the presence of detergents, an open conformation is observed, which probably represents the membrane-bound form. The selectivity of alpha-TTP for RRR-alpha-tocopherol is explained from the van der Waals contacts occurring in the lipid-binding pocket. Mapping the known mutations leading to AVED onto the crystal structure shows that no mutations occur directly in the binding pocket.
Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, 3012 Berne, Switzerland.