PROSITE documentation PDOC00416
Clostridium cellulosome enzymes repeated domain signature


Gram-positive, thermophilic anaerobes such as Clostridium thermocellum or Clostridium cellulolyticum secretes a highly active and thermostable cellulase complex (cellulosome) responsible for the degradation of crystalline cellulose [1,2]. The cellulosome contains at least 30 polypeptides, the majority of the enzymes are endoglucanases (EC, but there are also some xylanases (EC, β-glucosidases (EC and endo-β-1,3-1,4-glucanases (EC

Complete sequence data for many of these enzymes has been obtained. A majority of these proteins contain a highly conserved region of about 65 to 70 residues which is generally (but not always) located in the C-terminus. This region contains a duplicated segment of 24 amino acids. The function of this duplicated segment is not yet known, although it has been suggested that it could be involved in substrate-binding or in calcium-binding [3].

Currently this domain has been found in:

  • Endoglucanases A (celA), B (celB), D (celD), E (celE), F (celF), G (celG), H (celH) and X (celX) from Clostridium thermocellum.
  • Endoglucanases A (celCCA), C (celCCC), D (celCCD), F (celCCF) and G (celCCG) from Clostridium cellulolyticum.
  • Endoglucanase B (engB) from Clostridium cellulovorans.
  • Xylanases Y (XynY) and Z (xynZ) from Clostridium thermocellum.
  • Endo-β-1,3-1,4 glucanase (licB) from Clostridium thermocellum.
  • Cellulose integrating protein (cipA) from Clostridium thermocellum. CipA acts as a scaffolding protein in the cellulosome. It promotes binding of cellulose to the catalytic domains of the cellulolytic enzymes [4].

The pattern we developed spans the first 20 positions of the 24 amino acids segment.

Expert(s) to contact by email:

Beguin P.

Last update:

November 1997 / Text revised.


Technical section

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

CLOS_CELLULOSOME_RPT, PS00448; Clostridium cellulosome enzymes repeated domain signature  (PATTERN)


1AuthorsBeguin P.
TitleMolecular biology of cellulose degradation.
SourceAnnu. Rev. Microbiol. 44:219-248(1990).
PubMed ID2252383

2AuthorsBeguin P. Millet J. Aubert J.-P.
TitleCellulose degradation by Clostridium thermocellum: from manure to molecular biology.
SourceFEMS Microbiol. Lett. 79:523-528(1992).
PubMed ID1478480

3AuthorsChauvaux S. Beguin P. Aubert J.-P. Bhat K.M. Gow L.A. Wood T.M. Bairoch A.
TitleCalcium-binding affinity and calcium-enhanced activity of Clostridium thermocellum endoglucanase D.
SourceBiochem. J. 265:261-265(1990).
PubMed ID2302168

4AuthorsGerngross U.T. Romaniec M.P.M. Kobayashi T. Huskisson N.S. Demain A.L.
TitleSequencing of a Clostridium thermocellum gene (cipA) encoding the cellulosomal SL-protein reveals an unusual degree of internal homology.
SourceMol. Microbiol. 8:325-334(1993).
PubMed ID8316083

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