PROSITE documentation PDOC51159
CBM21 (carbohydrate binding type-21) domain profile


The carbohydrate binding type-21 or CBM21 domain is a 90-130 amino acid carbohydrate binding domain. The domain is named after proteins classified in carbohydrate-binding module (CBM) family 21 and is sometimes called starch-binding domain (SBD) [E1,1]. The CBM21 domain occurs in several eukaryotic proteins implicated in glycogen metabolism. A glucoamylase active site region (see <PDOC00646>) [E2] or α amylase catalytic domain [E3] 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 [2,3,4].

Some proteins known to contain a CBM21 domain:

  • Mammalian protein phosphatase 1 (PP1) regulatory subunit 3A, which seems to target PP1 to glycogen.
  • Mammalian protein phosphatase 1 binding protein PTG, which binds the 3 key enzymes for the regulation of glycogen metabolism: phosphorylase kinase, phosphorylase A and glycogen synthase.
  • Yeast protein phosphatase 1 regulatory subunits GAC1 and PIG1, which are regulators of glycogen synthase.
  • Yeast GLC7-interacting protein 2 (GIP2), which interacts with the catalytic subunit (GLC7) of PP1.
  • Yeast protein 2 interacting with GSY2 (PIG2), which interacts with glycogen synthase 2 (GSY2), a nutritionally regulated form.
  • Rhizopus oryzae glucoamylase, which binds and hydrolyzes granular starch. R. oryzae is a fungus from e.g. decaying vegetables and it causes mucormycosis.

The profile we developed covers the entire CBM21 domain.

Last update:

November 2005 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

CBM21, PS51159; CBM21 (carbohydrate binding type-21) domain profile  (MATRIX)


1AuthorsRodriguez-Sanoja R. Oviedo N. Sanchez S.
TitleMicrobial starch-binding domain.
SourceCurr. Opin. Microbiol. 8:260-267(2005).
PubMed ID15939348

2AuthorsCheng C. Huang D. Roach P.J.
TitleYeast PIG genes: PIG1 encodes a putative type 1 phosphatase subunit that interacts with the yeast glycogen synthase Gsy2p.
SourceYeast 13:1-8(1997).
PubMed ID9046081

3AuthorsPrinten J.A. Brady M.J. Saltiel A.R.
TitlePTG, a protein phosphatase 1-binding protein with a role in glycogen metabolism.
SourceScience 275:1475-1478(1997).
PubMed ID9045612

4AuthorsMachovic M. Svensson B. Ann Macgregor E. Janecek S.
TitleA new clan of CBM families based on bioinformatics of starch-binding domains from families CBM20 and CBM21.
SourceFEBS J. 272:5497-5513(2005).
PubMed ID16262690




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