Protein Domain : START domain IPR002913

Type	Domain
Description	START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins [ ]. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation [].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 ofsteroidogenesis. Representatives of the START domain family have been shown to bind different ligands such as sterols (StAR protein) andphosphatidylcholine (PC-TP). Ligand binding by the START domain can also regulate the activities of other domains that co-occur with the START domainin multidomain proteins such as Rho-gap, the homeodomain, and the thioesterase domain [, ]. The crystal structure of START domain of human MLN64 shows analpha/beta fold built around an U-shaped incomplete β-barrel. Most importantly, the interior of the protein encompasses a 26 x 12 x 11 Angstromshydrophobic tunnel that is apparently large enough to bind a single cholesterol molecule []. The START domain structure revealed an unexpectedsimilarity to that of the birch pollen allergen Bet v 1 and to bacterial polyketide cyclases/aromatases [, ].
Short Name	START_lipid-bd_dom