|PROSITE documentation PDOC00486 [for PROSITE entry PS51164]|
The microbial degradation of cellulose and xylans requires several types of enzymes such as endoglucanases (EC 18.104.22.168), cellobiohydrolases (EC 22.214.171.124) (exoglucanases), or xylanases (EC 126.96.36.199) . Cellulases and xylanases generally consist of a catalytic domain and a cellulose-binding domain (CBD) also called carbohydrate-binding module (CBM).
The carbohydrate-binding module of a number of fungal cellulases (CBM1) has been shown to consist of 38 amino acid residues. Enzymes known to contain such a domain are:
CBM1 is found either at the N-terminal (Cbh-II or egl2) or at the C-terminal extremity (Cbh-I, egl1 or egl5) of these enzymes. As it is shown in the following schematic representation, there are four conserved cysteines in this type of CBD domain, all involved in disulfide bonds. The CBM1 fold consists of a three-stranded antiparallel β-sheet (see <PDB:1AZJ>) . The domain folds into a wedge-shaped structure with a flat face containing three conserved aromatic residues separated by about 10.4 Angstroms which corresponds to the periodicity of the glucose units in the cellulose. These residues are thus probably involved in cellulose binding.
+----------------+ | +-----|---------+ | | | | xxxxxxxCxxxxxxxxxxCxxxxxCxxxxxxxxxCx ****************************
'C': conserved cysteine involved in a disulfide bond. '*': position of the pattern.
Such a domain has also been found in a putative polysaccharide binding protein from the red alga, Porphyra purpurea. Structurally, this protein consists of four tandem repeats of the CBD domain.Note:
CBM1 of endoglucanase I and exocellobiohydrolase II have a third disulfide bridge on their N-terminal side .Last update:
April 2006 / Pattern revised.
PROSITE methods (with tools and information) covered by this documentation:
|1||Authors||Gilkes N.R., Henrissat B., Kilburn D.G., Miller R.C. Jr., Warren R.A.J.|
|Title||Domains in microbial beta-1, 4-glycanases: sequence conservation, function, and enzyme families.|
|Source||Microbiol. Rev. 55:303-315(1991).|
|2||Authors||Mattinen M.L., Kontteli M., Kerovuo J., Linder M., Annila A., Lindeberg G., Reinikainen T., Drakenberg T.|
|Title||Three-dimensional structures of three engineered cellulose-binding domains of cellobiohydrolase I from Trichoderma reesei.|
|Source||Protein Sci. 6:294-303(1997).|
|3||Authors||Mattinen M.L., Linder M., Drakenberg T., Annila A.|
|Title||Solution structure of the cellulose-binding domain of endoglucanase I from Trichoderma reesei and its interaction with cello-oligosaccharides.|
|Source||Eur. J. Biochem. 256:279-286(1998).|