Structural highlights
Function
[S14L2_HUMAN] Carrier protein. Binds to some hydrophobic molecules and promotes their transfer between the different cellular sites. Binds with high affinity to alpha-tocopherol. Also binds with a weaker affinity to other tocopherols and to tocotrienols. May have a transcriptional activatory activity via its association with alpha-tocopherol. Probably recognizes and binds some squalene structure, suggesting that it may regulate cholesterol biosynthesis by increasing the transfer of squalene to a metabolic active pool in the cell.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
The vast majority of monomeric lipid transport in nature is performed by lipid-specific protein carriers. This class of proteins can enclose cognate lipid molecules in a hydrophobic cavity and transport them across the aqueous environment. Supernatant protein factor (SPF) is an enigmatic representative of monomeric lipid transporters belonging to the SEC14 family. SPF stimulates squalene epoxidation, a downstream step of the cholesterol biosynthetic pathway, by an unknown mechanism. Here, we present the three-dimensional crystal structure of human SPF in complex with RRR-alpha-tocopherylquinone, the major physiological oxidation product of RRR-alpha-tocopherol, at a resolution of 1.95A. The structure of the complex reveals how SPF sequesters RRR-alpha-tocopherylquinone (RRR-alpha-TQ) in its protein body and permits a comparison with the recently solved structure of human alpha-tocopherol transfer protein (alpha-TTP) in complex with RRR-alpha-tocopherol. Recent findings have shown that RRR-alpha-TQ is reduced in vivo to RRR-alpha-TQH(2), the latter has been suggested to protect low-density lipoprotein (LDL) particles from oxidation. Hence, the antioxidant function of the redox couple RRR-alpha-TQ/RRR-alpha-TQH(2) in blocking LDL oxidation may reduce cellular cholesterol uptake and thus explain how SPF upregulates cholesterol synthesis.
Supernatant protein factor in complex with RRR-alpha-tocopherylquinone: a link between oxidized Vitamin E and cholesterol biosynthesis.,Stocker A, Baumann U J Mol Biol. 2003 Sep 26;332(4):759-65. PMID:12972248[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Stocker A, Baumann U. Supernatant protein factor in complex with RRR-alpha-tocopherylquinone: a link between oxidized Vitamin E and cholesterol biosynthesis. J Mol Biol. 2003 Sep 26;332(4):759-65. PMID:12972248
