{PDOC50122}
{PS50122; CHEB}
{BEGIN}
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* CheB-type methylesterase domain profile *
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The response  regulator  CheB functions within the bacterial chemotaxis system
together with  the  methyltransferase  CheR  (see  <PDOC50123>) to control the
level of  chemoreceptor  methylation,  influencing the signaling activities of
the receptors.  Like many members of the response regulator family, CheB has a
multidomain architecture.   It  consists  of  an  N-terminal  phosphoaccepting
regulatory domain   with   a   conserved   fold   containing   the   site   of
phosphorylation, a single conserved aspartate residue (see <PDOC50110>), and a
C-terminal effector domain joined by a linker region. The effector domain is a
methylesterase (EC  3.1.1.61)  that catalyses the hydrolysis of gamma-carboxyl
glutamyl methyl esters in the cytoplasmic domain of chemoreceptor proteins [1,
2]. The  CheB  methylesterase domain belongs to the class of serine hydrolases
that contain  active site catalytic triads consisting of serine, histidine and
aspartate residues  [3].  Inhibition  of  methylesterase  activity  in  intact
unphosphorylated CheB  is  due  to partial occlusion of the active site by the
regulatory domain, thereby restricting access of the substrate chemoreceptors.
The phosphorylation  of the regulatory domain results in reorganization of the
domain interface,  allowing  exposure  of  the  active  site  to  the receptor
substrate [4,5].

The crystal  structure  of  the Salmonella typhimurium CheB methylesterase has
been solved.  The  structure  of the CheB methylesterase domain is composed of
six alpha-helices and nine beta-strands with an overall alpha/beta fold common
for globular proteins that can be classified as a slight variation of a doubly
wound alpha/beta  domain.  The  core  of  the  molecules  consists of a seven-
stranded parallel beta-sheet and is flanked by three alpha-helices on one side
and three  alpha-helices  plus  an  antiparallel  beta-hairpin  motif  on  the
opposite side of the sheet [3,4].

The profile we developed covers the entire CheB methylesterase domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: January 2002 / First entry.

[ 1] Simms S.A., Keane M.G., Stock J.
     "Multiple forms of the CheB methylesterase in bacterial
     chemosensing."
     J. Biol. Chem. 260:10161-10168(1985).
     PubMed=2991277
[ 2] Lupas A., Stock J.
     "Phosphorylation of an N-terminal regulatory domain activates the CheB
     methylesterase in bacterial chemotaxis."
     J. Biol. Chem. 264:17337-17342(1989).
     PubMed=2677005
[ 3] West A.H., Martinez-Hackert E., Stock A.M.
     "Crystal structure of the catalytic domain of the chemotaxis receptor
     methylesterase, CheB."
     J. Mol. Biol. 250:276-290(1995).
     PubMed=7608974
[ 4] Djordjevic S., Goudreau P.N., Xu Q., Stock A.M., West A.H.
     "Structural basis for methylesterase CheB regulation by a
     phosphorylation-activated domain."
     Proc. Natl. Acad. Sci. U.S.A. 95:1381-1386(1998).
     PubMed=9465023
[ 5] Anand G.S., Goudreau P.N., Stock A.M.
     "Activation of methylesterase CheB: evidence of a dual role for the
     regulatory domain."
     Biochemistry 37:14038-14047(1998).
     PubMed=9760239; DOI=10.1021/bi980865d

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