START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins PMID:10322415. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation PMID:7961770. 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 PMID:10322415,PMID:11276083. The crystal structure of START domain of human MLN64 shows an alpha/beta fold built around an U-shaped incomplete beta-barrel PMID:10802740. This superfamily represents an alpha/beta sandwich structural domain found in a wide variety of protein families, including STAR-related lipid transfer proteins and homeobox-leucine zipper proteins.

PMID:10322415 PMID:10322415 PMID:11276083 PMID:10802740 (INTERPRO:IPR023393)