PROSITE documentation PDOC50848
START domain profile


The StAR-related lipid-transfer (START) domain is an about 200-210 residue lipid-binding motif, which is primarily involved in eukaryotic signaling mediated by lipid binding. 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 (see <PDOC00027>), and the thioesterase domain [1,2].

The crystal structure of START domain of human MLN64 (see <PDB:1EM2>) shows an α/β fold built around an U-shaped incomplete β-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 [3,4]. The START domain structure revealed an unexpected similarity to that of the birch pollen allergen Bet v 1 and to bacterial polyketide cyclases/aromatases [2,3].

Some proteins known to contain a START domain are listed below:

  • Mammalian steroidogenic acute regulatory protein (StAR) orthologues. StAR can somehow mediate cholesterol transfer to the inner mitochondrial membrane. In human, mutations in the gene that encodes StAR causes congenital adrenal hyperplasia (lipoid CAH).
  • Mammalian phosphatidylcholine transfer protein (PC-TP).
  • Mammalian RHOA-specific GTPase-activating protein (RhoGAP).
  • Mammalian Goodpasture antigen binding protein.
  • Vertebrate acyl-CoA thioesterase.
  • Plant proteins from the Glabra2 (Gla2) family. The Gla2 homeodomain protein is involved in regulating trichome morphogenesis and root-hair development.
  • Dictyostelium discoideum CheaterA (ChtA) protein. Mutations in the gene that encodes ChtA induce the preferential formation of spores rather than stalk.
  • Pseudomonas aeruginosa hypothetical protein PA1579. This protein is closely related to the animal PC-binding proteins, which suggests horizontal acquisition from animals. It seems likely that the START domain of this protein plays a role in the interaction of the bacterium with animal cells.

The profile we developed covers the entire START domain.

Last update:

May 2002 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

START, PS50848; START domain profile  (MATRIX)


1AuthorsPonting C.P. Aravind L.
TitleSTART: a lipid-binding domain in StAR, HD-ZIP and signalling proteins.
SourceTrends Biochem. Sci. 24:130-132(1999).
PubMed ID10322415

2AuthorsIyer L.M. Koonin E.V. Aravind L.
TitleAdaptations of the helix-grip fold for ligand binding and catalysis in the START domain superfamily.
SourceProteins 43:134-144(2001).
PubMed ID11276083

3AuthorsTsujishita Y. Hurley J.H.
TitleStructure and lipid transport mechanism of a StAR-related domain.
SourceNat. Struct. Biol. 7:408-414(2000).
PubMed ID10802740

4AuthorsStocco D.M.
TitleStARTing to understand cholesterol transfer.
SourceNat. Struct. Biol. 7:445-447(2000).
PubMed ID10881186

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