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141  structures 7089  species 0  interactions 30982  sequences 353  architectures

Family: STAS (PF01740)

Summary: STAS domain

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STAS domain Provide feedback

The STAS (after Sulphate Transporter and AntiSigma factor antagonist) domain is found in the C terminal region of Sulphate transporters and bacterial antisigma factor antagonists. It has been suggested that this domain may have a general NTP binding function [2].

Literature references

  1. Kovacs H, Comfort D, Lord M, Campbell ID, Yudkin MD; , Proc Natl Acad Sci U S A 1998;95:5067-5071.: Solution structure of SpoIIAA, a phosphorylatable component of the system that regulates transcription factor sigmaF of Bacillus subtilis. PUBMED:9560229 EPMC:9560229

  2. Aravind L, Koonin EV; , CurrBiol 2000;10:53-55.: The STAS domain - a link between anion transporters and antisigma-factor antagonists PUBMED:10662676 EPMC:10662676

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR002645

The STAS (Sulphate Transporter and AntiSigma factor antagonist) domain is found in the bacterial anti-sigma factor antagonists (ASA) and the C-terminal region of SLC26 (SulP) anion transporters.

The activity of bacterial sigma transcription factors is controlled by a regulatory cascade involving an antisigma-factor, the antisigma-factor antagonist (ASA) and a phosphatase. The antisigma-factor binds to sigma and holds it in an inactive complex. The ASA can also interact with the anti-sigma-factor, allowing the release of the active sigma factor. As the antisigma-factor is a protein kinase, it can phosphorylate the antisigma antagonist on a conserved serine residue of the STAS domain. This phosphorylation inactivates the ASA that can be reactivated through dephosphorylation by a phosphatase [ PUBMED:10662676 , PUBMED:10476035 ]. The STAS domain of the ASA SpoIIAA binds GTP and ATP and possesses a weak NTPase activity. Strong sequence conservation suggests that the STAS domain could possess general NTP-binding activity, and it has been proposed that the NTPs are likely to elicit specific conformational changes in the STAS domain through binding and/or hydrolysis [ PUBMED:10662676 ]. Resolution of the solution structure of the ASA SpoIIAA from Bacillus subtilis has shown that the STAS domain consists of a four-stranded beta-sheet and four alpha helices. The STAS domain forms a characteristic alpha-helical handle-like structure [ PUBMED:10662676 , PUBMED:9560229 ].

The STAS domain of E. coli YchM protein, a SLC26 (SulP) family member, has been shown to interact with acyl carrier protein (ACP), which is an activated thiol ester carrier of acyl intermediates during fatty acid biosynthesis (FAB) and other acylation reactions [ PUBMED:21070944 ].

Malfunctions in members of the SLC26A family of anion transporters are involved in three human diseases: diastrophic dysplasia/achondrogenesis type 1B (DTDST), Pendred's syndrome (PDS) and congenital chloride diarrhea (CLD). These proteins contain 12 transmembrane helices followed by a cytoplasmic STAS domain at the C terminus. The importance of the STAS domain in these transporters is illustrated by the fact that a number of mutations in PDS and DTDST map to it [ PUBMED:10662676 , PUBMED:22116355 ].

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 STAS (CL0502), which has the following description:

This superfamily includes proteins that have a STAS domain.

The clan contains the following 4 members:

DUF4325 SpoIIAA-like STAS STAS_2


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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Curation View help on the curation process

Seed source: [2]
Previous IDs: SpoIIAA;
Type: Domain
Sequence Ontology: SO:0000417
Author: Bateman A
Number in seed: 68
Number in full: 30982
Average length of the domain: 115.80 aa
Average identity of full alignment: 16 %
Average coverage of the sequence by the domain: 24.85 %

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 22.6 22.6
Trusted cut-off 22.6 22.6
Noise cut-off 22.5 22.5
Model length: 117
Family (HMM) version: 23
Download: download the raw HMM for this family

Species distribution

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Colour assignments

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 STAS domain has been found. There are 141 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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