PROSITE documentation PDOC52005

CBM56 (carbohydrate binding type-56) domain profile

Carbohydrate binding modules (CBMs) are independent domains existing in carbohydrate active enzymes. The majority of such domains exhibit carbohydrate binding activity, which enhances the catalytic efficiency of carbohydrate active enzymes. The non-catalytic CBMs are classified into families, which currently number >70 and are based on amino acid sequence identity. The CBM family 56 (CBM56) domain is an ~95-amino acid module, which selectively binds insoluble β-1,3-glucans, probably by binding domains in the polysaccharide with triple-helical quaternary structure [1,2,3,4,E1].

The CBM56 domain adopts a β-sandwich fold comprising two opposing 4-stranded β-sheets with the very last β-strand in the fold being broken up by a bulge in its middle (see <PDB:5T7A>) [1].

Some proteins known to contain a CBM56 domain are listed below:

• Bacillus halodurans BH0236, a multimodular β-1,3-glucanase comprising an N-terminal family 81 glycoside hydrolase (GH) catalytic module, an internal family 6 carbohydrate-binding module (CBM) (see <PDOC51175>) that binds the nonreducing end of β-1,3-glucan chains, and a C-terminal CBM56 domain [1].
• Paenibacillus barengoltzii GH family 64 β-1,3-glucanase (PbBgl64A), a multi-domain protein that belongs to the GH64-TLP superfamily, which consists of an N-terminal CBM56 domain and a C-terminal family 64 GH domain [2,3].
• Clostridium beijerinckii glucanallin, composed of a βγ-crystallin domain (see <PDOC00197>), a GH64 domain, and a CBM56 domain [4].

The profile we developed covers the whole CBM56 domain.