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- ******************************************************
- * Bacterial chemotaxis sensory transducers signature *
- ******************************************************
-
- 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.
-
- -Consensus pattern: R-T-E-[EQ]-Q-x(2)-[SA]-[LIVM]-x-[EQ]-T-A-A-S-M-E-Q-L-T-A-
- T-V
- [The two E/Q position and the last Q are all sites of
- reversible methylation]
- -Sequences known to belong to this class detected by the pattern: ALL.
- -Other sequence(s) detected in SWISS-PROT: NONE.
- -Last update: October 1993 / Text revised.
-
- [ 1] Stewart R.C., Dahlquist F.W.
- Chem. Rev. 87:997-1025(1987).
- [ 2] Hazelbauer G.L.
- Can. J. Microbiol. 34:466-474(1988).
- [ 3] Dahl M.K., Boos W., Manson M.D.
- J. Bacteriol. 171:2361-2371(1989).
- [ 4] Yamamoto K., Imae Y.
- Proc. Natl. Acad. Sci. U.S.A. 90:217-221(1993).
- [ 5] Rice M.S., Dahlquist F.W.
- J. Biol. Chem. 266:9746-9753(1991).
-