α-TOCOPHEROL TRANSFER PROTEIN (αTTP)

32 kDa protein

Highly expressed in liver, but very small amounts in brain, retina, lymphocytes
Fibroblasts, and placenta
Relative affinities for tocopherol isomers

• α-tocopherol 100%
• β-tocopherol 38%
• γ-tocopherol 9%
• α-tocotrienol 12%

Main function in hepatocytes is to selectively transfer α-tocopherol from ER to VLDL in the Golgi apparatus.

Mutations in TTP lead to vitamin E deficiency and cause disease such as ataxia.
(Ataxia is a nervous system disease leading to severe lack of muscle coordination. The conditions can affect arms and legs, fingers, body, speech and eye movements.)

Figure
The ligand binding pocket of αTTP has a high affinity for α-tocopherol, but not for γ-tocopherol.

OTHER PROTEINS:

See Tocopherol associated proteins (TAP) in the menu items.