PROSITE documentation PDOC00465
Bacterial chemotaxis sensory transducers signature and profile


Bacterial chemotactic-signal transducers [1,2] are proteins that respond to changes in the concentration of attractants and repellents in the environment, and transduce a signal from the outside to the inside of the cell. These proteins undergo two covalent modifications: deamidation and reversible methylation. 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.

In Escherichia coli and related bacteria, there are four different chemotactic transducers:

  • tsr, responsible for taxis to the attractants L-serine and related amino acids and away from the repellents leucine, indole, and weak acids.
  • tar, responsible for taxis to the attractants L-aspartate and related amino and dicarboxylic acids. Also mediates taxis to the attractant maltose via an interaction with the periplasmic maltose-binding protein. Mediates taxis away from the repellents cobalt and nickel.
  • trg, responsible for taxis to ribose and galactose via an interaction with the periplasmic ribose- or galactose-binding proteins.
  • tap, responsible for taxis towards dipeptides via an interaction with the periplasmic dipeptide-binding protein.

In Enterobacter aerogenes [3] there are at least two different chemotactic transducers:

  • tsr, responsible for taxis to the attractant L-serine.
  • tas, responsible for taxis to the attractant L-aspartate.

In Salmonella typhimurium [4], in addition to tar, there is:

  • tcp, responsible for taxis to the attractant citrate.

All these proteins are composed of the same structural domains: a N-terminal region that resembles a signal peptide, but which is not removed from the mature protein and serves as a membrane-spanning region; a periplasmic domain of about 160 amino acids that forms the receptor domain; a second transmembrane region and finally a C-terminal cytoplasmic domain of about 300 amino acids which contains the methylation sites.

The methyl-accepting sites are specific glutamate residues (some of these sites are translated as glutamine but are irreversibly deamidated by cheB). They are clustered in two regions of the cytoplasmic domain [5]. As a signature pattern we have selected the first of these two regions.

Last update:

September 2002 / text revised; profile added.


Technical section

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

CHEMOTAXIS_TRANSDUC_2, PS50111; Bacterial chemotaxis sensory transducers domain profile  (MATRIX)

CHEMOTAXIS_TRANSDUC_1, PS00538; Bacterial chemotaxis sensory transducers signature  (PATTERN)


1AuthorsStewart R.C. Dahlquist F.W.
SourceChem. Rev. 87:997-1025(1987).

2AuthorsHazelbauer G.L.
TitleThe bacterial chemosensory system.
SourceCan. J. Microbiol. 34:466-474(1988).
PubMed ID3052756

3AuthorsDahl M.K. Boos W. Manson M.D.
TitleEvolution of chemotactic-signal transducers in enteric bacteria.
SourceJ. Bacteriol. 171:2361-2371(1989).
PubMed ID2496104

4AuthorsYamamoto K. Imae Y.
TitleCloning and characterization of the Salmonella typhimurium-specific chemoreceptor Tcp for taxis to citrate and from phenol.
SourceProc. Natl. Acad. Sci. U.S.A. 90:217-221(1993).
PubMed ID8419927

5AuthorsRice M.S. Dahlquist F.W.
TitleSites of deamidation and methylation in Tsr, a bacterial chemotaxis sensory transducer.
SourceJ. Biol. Chem. 266:9746-9753(1991).
PubMed ID2033064

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