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33  structures 465  species 0  interactions 1565  sequences 52  architectures

Family: TarH (PF02203)

Summary: Tar ligand binding domain homologue

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This is the Wikipedia entry entitled "Aspartate receptor". More...

Aspartate receptor Edit Wikipedia article

Tar ligand binding domain homologue
Ligand binding domain aspartate receptor.png
Ribbon diagram of the S. typhimurium aspartate receptor ligand binding domain[1]

The aspartate receptor, Tar, is a member of a family of transmembrane receptors that mediate chemotactic response in certain enteric bacteria, such as Salmonella typhimurium and Escherichia coli.[2] These methyl-accepting chemotaxis receptors are one of the first components in the sensory excitation and adaptation responses in bacteria, which act to alter swimming behaviour upon detection of specific chemicals. The aspartate receptor mediates movement towards the attractants aspartate and maltose, and away from the repellents nickel and cobalt. There are many different types of bacterial 60 kDa transmembrane receptors, which share similar topology and signalling mechanisms. They possess three domains: a periplasmic ligand-binding domain, two transmembrane segments, and a cytoplasmic domain. The structure of the ligand-binding domain comprises a closed or partly opened, four-helical bundle with a left-handed twist. The difference in the sequence of the ligand-binding domain between receptors reflects the different ligand specificities. Binding of the ligand causes a conformational change that is transmitted across the membrane to the cytoplasmic activation domain.[3]


  1. ^ PDB: 1VLT​; Yeh JI, Biemann HP, Privé GG, Pandit J, Koshland DE Jr, Kim SH (1996). "High-resolution structures of the ligand binding domain of the wild-type bacterial aspartate receptor". J Mol Biol. 262: 186–201. doi:10.1006/jmbi.1996.0507. PMID 8831788.; rendered with PyMOL
  2. ^ Kim SH, Prive GG, Pandit J, Koshland DE, Yeh JI, Biemann HP (1996). "High-resolution structures of the ligand binding domain of the wild-type bacterial aspartate receptor". J. Mol. Biol. 262 (2): 186–201. doi:10.1006/jmbi.1996.0507. PMID 8831788.
  3. ^ Koshland DE, Yu EW (2001). "Propagating conformational changes over long (and short) distances in proteins". Proc. Natl. Acad. Sci. U.S.A. 98 (17): 9517–9520. doi:10.1073/pnas.161239298. PMC 55484. PMID 11504940.
This article incorporates text from the public domain Pfam and InterPro: IPR003122

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Tar ligand binding domain homologue Provide feedback

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External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR003122

Methyl-accepting chemotaxis proteins (MCPs) are a family of bacterial receptors that mediate chemotaxis to diverse signals, responding to changes in the concentration of attractants and repellents in the environment by altering swimming behaviour [ PUBMED:16359703 ]. Environmental diversity gives rise to diversity in bacterial signalling receptors, and consequently there are many genes encoding MCPs [ PUBMED:17299051 ]. For example, there are four well-characterised MCPs found in Escherichia coli: Tar (taxis towards aspartate and maltose, away from nickel and cobalt), Tsr (taxis towards serine, away from leucine, indole and weak acids), Trg (taxis towards galactose and ribose) and Tap (taxis towards dipeptides).

MCPs share similar topology and signalling mechanisms. MCPs either bind ligands directly or interact with ligand-binding proteins, transducing the signal to downstream signalling proteins in the cytoplasm. MCPs undergo two covalent modifications: deamidation and reversible methylation at a number of glutamate residues. Attractants increase the level of methylation, while repellents decrease it. The methyl groups are added by the methyl-transferase cheR and are removed by the methylesterase cheB. Most MCPs are homodimers that contain the following organisation: an N-terminal signal sequence that acts as a transmembrane domain in the mature protein; a poorly-conserved periplasmic receptor (ligand-binding) domain; a second transmembrane domain; and a highly-conserved C-terminal cytoplasmic domain that interacts with downstream signalling components. The C-terminal domain contains the glycosylated glutamate residues.

This entry represents the ligand-binding domain found in a number of methyl-accepting chemotaxis receptors, such as E.coli Tar (taxis to aspartate and repellents), which is a receptor for the attractant L-aspartate [ PUBMED:1660187 , PUBMED:27292793 ]. It is a homodimeric receptor that contains an N-terminal periplasmic ligand binding domain, a transmembrane region, a HAMP domain and a C-terminal cytosolic signaling domain [ PUBMED:21689529 ].

Gene Ontology

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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 4HB_MCP (CL0457), which has the following description:

This superfamily is characterised by a four-helix bundle structure that forms a ubiquitous sensory module in prokaryotic signal-transduction. The 4HB_MCP is always found between two predicted transmembrane helices indicating that it detects only extracellular signals. In many cases the domain is associated with a cytoplasmic HAMP domain suggesting that most proteins carrying the bundle might share the mechanism of transmembrane signalling which is well-characterised in E coli chemoreceptors.

The clan contains the following 4 members:



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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: 67
Number in full: 1565
Average length of the domain: 169.50 aa
Average identity of full alignment: 16 %
Average coverage of the sequence by the domain: 30.87 %

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 25.2 23.0
Trusted cut-off 25.2 23.5
Noise cut-off 25.1 22.9
Model length: 177
Family (HMM) version: 17
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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 TarH domain has been found. There are 33 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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AlphaFold Structure Predictions

The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.

Protein Predicted structure External Information
P02942 View 3D Structure Click here
P05704 View 3D Structure Click here
P07017 View 3D Structure Click here
P07018 View 3D Structure Click here