INTRACELLULAR TRANSPORT

Cytoplasmic proteins that bind tocopherol:

For retention of α-tocopherol:

• α-tocopherol transfer protein (αTTP - 32 kDa)

For distribution of tocopherol:

• Tocopherol binding protein (TBP - 15 kDa)
• Tocopherol associated proteins (TAPs - 46 kDa)

Figure
Overview of intracellular transport of tocopherols (represented by dots), and the role of the different proteins αTTP, TBP, and TAPs

Vitamin E bound to chylomicron remnant is taken up by the LDL receptor (LDLR), and HDL-bound α-tocopherol by the scavenger receptor BI (SR-BI).

The main role of αTTP is to transfer α-tocopherol from ER to VLDL in the Golgi apparatus (see later).

TBP and TAPs redirects tocopherols to different cell compartments in endosomes (see later).