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Impaired α-TTP-PIPs Interaction Underlies Familial Vitamin E Deficiency

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Science  18 Apr 2013:
1233508
DOI: 10.1126/science.1233508

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Abstract

α-Tocopherol (vitamin E) transfer protein (α-TTP) regulates the secretion of α-tocopherol from liver cells. Missense mutations of some arginine residues at the surface of α-TTP cause severe vitamin E deficiency in humans, but the role of these residues is unclear. Here, we found that wild-type α-TTP bound phosphatidylinositol phosphates (PIPs), whereas the arginine mutants did not. In addition, PIPs in the target membrane promoted the intermembrane transfer of α-tocopherol by α-TTP. The crystal structure of the α-TTP-PIPs complex revealed that the disease-related arginine residues interacted with phosphate groups of the PIPs and that the PIPs binding caused the lid of the α-tocopherol-binding pocket to open. Thus, PIPs have a role in promoting the release of a ligand from a lipid-transfer protein.

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