{PDOC51175}
{PS51175; CBM6}
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* CBM6 (carbohydrate binding type-6) domain profile *
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Carbohydrate-binding  modules  (CBM)  have  been  classified into more than 40
families  according  to  sequence  homology [E1]. Several cellulolytic enzymes
share  a  conserved  region  of about 120 amino acid residues, the CBM6 domain
[1].  The CBM6 domain is distinct from others CBMs in that this protein module
contains  multiple  distinct  ligand  binding  sites.  CBM6  domains  bind  to
amorphous  cellulose,  xylan,  mixed beta-(1,3)(1,4)glucan and beta-1,3-glucan
[1,2,3].

The  CBM6  domain  is  mainly  found C-terminal to the catalytic domain, which
corresponds to a wide range of bacterial glycosyl hydrolases such as family 16
(see <PDOC00794>), or family 10 (see <PDOC00510>).

The  crystal structure of CBM6 domain has been solved (see <PDB:1GMM>) [4]. It
adopts a classic lectin-like beta-jelly roll fold, predominantly consisting of
five  antiparallel beta-strands on one face and four antiparallel beta-strands
on  the  other  face.  It  contains  two potential ligand binding sites, named
respectively  cleft  A and B. These clefts include aromatic residues which are
probably  involved  in  the  substrate  binding. The cleft B is located on the
concave  surface of one beta-sheet, and the cleft A on one edge of the protein
between  the  loop  that connects the inner and outer beta-sheets of the jelly
roll  fold  [4].  The  multiple  binding  clefts confer the extensive range of
specificities displayed by the domain [1,2,3].

Some proteins known to contain a CBM6 domain are listed below:

 - The  bacterial  Endo-1,4-beta-xylanase A, B, C, E, J, U, V, Y and Z  (xynA,
   xynB, xynC, xynE, xynJ, xynU, xynV, xynY, and xynZ). They are  involved  in
   the  endohydrolysis  of 1,4-beta-D-xylosidic linkages in xylans (EC 3.2.1.8
   and EC 3.2.1.55).
 - The  Piromyces sp. Mannan endo-1,4-beta-mannosidase A (manA) (EC 3.2.1.78).

The profile we developed covers the whole CBM6 domain.

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

-Note: The  CBM6  domain  is also known as  cellulose-binding domain family VI
 (CBD VI).

-Last update: December 2005 / First entry.

[ 1] van Bueren A.L., Morland C., Gilbert H.J., Boraston A.B.
     "Family 6 carbohydrate binding modules recognize the non-reducing end
     of beta-1,3-linked glucans by presenting a unique ligand binding
     surface."
     J. Biol. Chem. 280:530-537(2005).
     PubMed=15501830; DOI=10.1074/jbc.M410113200
[ 2] Henshaw J.L., Bolam D.N., Pires V.M.R., Czjzek M., Henrissat B.,
     Ferreira L.M.A., Fontes C.M.G.A., Gilbert H.J.
     "The family 6 carbohydrate binding module CmCBM6-2 contains two
     ligand-binding sites with distinct specificities."
     J. Biol. Chem. 279:21552-21559(2004).
     PubMed=15004011; DOI=10.1074/jbc.M401620200
[ 3] Pires V.M.R., Henshaw J.L., Prates J.A.M., Bolam D.N., Ferreira L.M.A.,
     Fontes C.M.G.A., Henrissat B., Planas A., Gilbert H.J., Czjzek M.
     "The crystal structure of the family 6 carbohydrate binding module
     from Cellvibrio mixtus endoglucanase 5a in complex with
     oligosaccharides reveals two distinct binding sites with different
     ligand specificities."
     J. Biol. Chem. 279:21560-21568(2004).
     PubMed=15010454; DOI=10.1074/jbc.M401599200
[ 4] Czjzek M., Bolam D.N., Mosbah A., Allouch J., Fontes C.M.G.A.,
     Ferreira L.M.A., Bornet O., Zamboni V., Darbon H., Smith N.L.,
     Black G.W., Henrissat B., Gilbert H.J.
     "The location of the ligand-binding site of carbohydrate-binding
     modules that have evolved from a common sequence is not conserved."
     J. Biol. Chem. 276:48580-48587(2001).
     PubMed=11673472; DOI=10.1074/jbc.M109142200
[E1] http://www.cazy.org/CBM6.html

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