STARTin StAR and phosphatidylcholine transfer protein
|SMART accession number:||SM00234|
|Description:||putative lipid-binding domain in StAR and phosphatidylcholine transfer protein|
|Interpro abstract (IPR002913):|
START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins [(PUBMED:10322415)]. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation [(PUBMED:7961770)]. Expression of the protein in the absence of hormone stimulation is sufficient to induce steroid production, suggesting that this protein is required in the acute regulation of steroidogenesis. Representatives of the START domain family have been shown to bind different ligands such as sterols (StAR protein) and phosphatidylcholine (PC-TP). Ligand binding by the START domain can also regulate the activities of other domains that co-occur with the START domain in multidomain proteins such as Rho-gap, the homeodomain, and the thioesterase domain [(PUBMED:10322415), (PUBMED:11276083)].
The crystal structure of START domain of human MLN64 shows an alpha/beta fold built around an U-shaped incomplete beta-barrel. Most importantly, the interior of the protein encompasses a 26 x 12 x 11 Angstroms hydrophobic tunnel that is apparently large enough to bind a single cholesterol molecule [(PUBMED:10802740)]. The START domain structure revealed an unexpected similarity to that of the birch pollen allergen Bet v 1 and to bacterial polyketide cyclases/aromatases [(PUBMED:11276083), (PUBMED:10802740)].
|GO function:||lipid binding (GO:0008289)|
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