{PDOC00465}
{PS00538; CHEMOTAXIS_TRANSDUC_1}
{PS50111; CHEMOTAXIS_TRANSDUC_2}
{BEGIN}
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* Bacterial chemotaxis sensory transducers signature and profile *
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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.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Last update: September 2002 / text revised; profile added.

[ 1] Stewart R.C., Dahlquist F.W.
     Chem. Rev. 87:997-1025(1987).
[ 2] Hazelbauer G.L.
     "The bacterial chemosensory system."
     Can. J. Microbiol. 34:466-474(1988).
     PubMed=3052756
[ 3] Dahl M.K., Boos W., Manson M.D.
     "Evolution of chemotactic-signal transducers in enteric bacteria."
     J. Bacteriol. 171:2361-2371(1989).
     PubMed=2496104
[ 4] Yamamoto K., Imae Y.
     "Cloning and characterization of the Salmonella typhimurium-specific
     chemoreceptor Tcp for taxis to citrate and from phenol."
     Proc. Natl. Acad. Sci. U.S.A. 90:217-221(1993).
     PubMed=8419927
[ 5] Rice M.S., Dahlquist F.W.
     "Sites of deamidation and methylation in Tsr, a bacterial chemotaxis
     sensory transducer."
     J. Biol. Chem. 266:9746-9753(1991).
     PubMed=2033064

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