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64  structures 1204  species 0  interactions 15238  sequences 230  architectures

Family: START (PF01852)

Summary: START domain

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This is the Wikipedia entry entitled "StAR-related transfer domain". More...

StAR-related transfer domain Edit Wikipedia article

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START domain Provide feedback

No Pfam abstract.

Literature references

  1. Ponting CP, Aravind L; , Trends Biochem Sci 1999;24:130-132.: START: a lipid-binding domain in StAR, HD-ZIP and signalling proteins. PUBMED:10322415 EPMC:10322415

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry 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 ].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan Bet_v_1_like (CL0209), which has the following description:

The Pfam:PF00407 entry is composed of sequences related to the major Birch (Betula verrucose) pollen antigen Bet v 1. This allergen is known to cause hayfever, dermatitis, asthma and occasionally anaphylactic shock. The other families in this clan share the same structure as Bet v 1, which is composed of antiparallel beta sheets and alpha helices. There is a cavity between the beta sheet and a long C terminal helix. The cavity appears to play roles in the binding of lipid molecules [1][2][3] which seems a common feature of the families in this clan.

The clan contains the following 24 members:

AHSA1 Aromatic_hydrox Bet_v_1 COXG DAPG_hydrolase DUF1857 DUF2505 DUF3074 DUF3211 DUF3284 Fungal_KA1 IP_trans KshA_C LigXa_C Lipoprotein_18 PaO Polyketide_cyc Polyketide_cyc2 PRELI Ring_hydroxyl_A START START_2 VanA_C VASt


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

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This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

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Curation and family details

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Seed source: Alignment kindly provided by SMART
Previous IDs: none
Type: Domain
Sequence Ontology: SO:0000417
Author: SMART
Number in seed: 16
Number in full: 15238
Average length of the domain: 188.20 aa
Average identity of full alignment: 16 %
Average coverage of the sequence by the domain: 29.55 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.6 20.6
Trusted cut-off 20.6 20.6
Noise cut-off 20.5 20.5
Model length: 209
Family (HMM) version: 21
Download: download the raw HMM for this family

Species distribution

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Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the START domain has been found. There are 64 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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