TTPa encodes a soluble protein that binds alpha-trocopherol, a form of vitamin E, with high selectivity and affinity. This protein plays an important role in regulating vitamin E levels in the body by transporting vitamin E between membrane vesicles and facilitating the secretion of vitamin E from hepatocytes to circulating lipoproteins. Mutations in this gene cause hereditary vitamin E deficiency (ataxia with vitamin E deficiency, AVED) and retinitis pigmentosa.

Using rat alpha-Ttp to screen a liver cDNA library, followed by PCR, Arita et al. (1995) cloned full-length human alpha-TTP. The deduced 278-amino acid protein has a calculated molecular mass of 31.7 kD and shares 94% identity with rat alpha-Ttp. Northern blot analysis of several human tissues detected a 4.5-kb alpha-TTP transcript in liver only.