InterPro domain: IPR038175

The carbohydrate binding type-21 or CBM21 domain is a 90-130 amino acidcarbohydrate binding domain. The domain is named after proteins classified incarbohydrate-binding module (CBM) family 21 and is sometimes called starch-binding domain (SBD) [ 1 ]. The CBM21 domain occurs in several eukaryotic proteins implicated in glycogen metabolism. A glucoamylase active site region or alpha amylase catalytic domain can occur C-terminal to the CBM21 domain. The CBM21 domain of Rhizopus oryzae glucoamylase can bind to raw starch. Most conserved residues are located in a region with a length of 35 in the N-terminal part [ 2 ] and in a 15-25 residue motif II at the C terminus of the domain [ 3 , 3 , 4 ].

1. Microbial starch-binding domain. Curr. Opin. Microbiol. 8, 260-7
2. Yeast PIG genes: PIG1 encodes a putative type 1 phosphatase subunit that interacts with the yeast glycogen synthase Gsy2p. Yeast 13, 1-8
3. PTG, a protein phosphatase 1-binding protein with a role in glycogen metabolism. Science 275, 1475-8
4. A new clan of CBM families based on bioinformatics of starch-binding domains from families CBM20 and CBM21. FEBS J. 272, 5497-513