Domain

Carbohydrate binding module family 6 (IPR005084)

Short name: CMB_fam6

Domain relationships

Description

A carbohydrate-binding module (CBM) is defined as a contiguous amino acid sequence within a carbohydrate-active enzyme with a discreet fold having carbohydrate-binding activity. A few exceptions are CBMs in cellulosomal scaffolding proteins and rare instances of independent putative CBMs. The requirement of CBMs existing as modules within larger enzymes sets this class of carbohydrate-binding protein apart from other non-catalytic sugar binding proteins such as lectins and sugar transport proteins.

CBMs were previously classified as cellulose-binding domains (CBDs) based on the initial discovery of several modules that bound cellulose [PMID: 3338453, PMID: 3134347]. However, additional modules in carbohydrate-active enzymes are continually being found that bind carbohydrates other than cellulose yet otherwise meet the CBM criteria, hence the need to reclassify these polypeptides using more inclusive terminology.

Previous classification of cellulose-binding domains were based on amino acid similarity. Groupings of CBDs were called "Types" and numbered with roman numerals (e.g. Type I or Type II CBDs). In keeping with the glycoside hydrolase classification, these groupings are now called families and numbered with Arabic numerals. Families 1 to 13 are the same as Types I to XIII. For a detailed review on the structure and binding modes of CBMs see [PMID: 15214846].

This entry represents CBM6 which was previously known as cellulose-binding domain family VI (CBD VI). CBM6 bind to amorphous cellulose, xylan, mixed beta-(1,3)(1,4)glucan and beta-1,3-glucan[PMID: 15501830, PMID: 15004011, PMID: 15010454].

CBM6 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 jellyroll fold [PMID: 11673472]. The multiple binding clefts confer the extensive range of specificities displayed by the domain [PMID: 15501830, PMID: 15004011, PMID: 15010454].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0030246 carbohydrate binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam
Pfam
PROSITE profiles