InterPro: IPR018242 Dockerin type 1

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:3.2.1.4), but there are also some xylanases (EC:3.2.1.8), beta-glucosidases (EC:3.2.1.21) and endo-beta-1,3-1,4-glucanases (EC:3.2.1.73).

Complete sequence data for many of these enzymes has been obtained. A majority of these proteins contain a highly conserved type I dockerin domain of about 65 to 70 residues, which is generally (but not always) located in the C terminus. The dockerin domain is the binding partner of the cohesin domain (see IPR002102). The cohesin-dockerin interaction is the crucial interaction for complex formation in the cellulosome [3]. The dockerin domain contains a tandem repeat of two calcium-binding loop-helix motifs (distinct from EF-hand Ca-binding motifs). These motifs are about 24 amino acids in length. This entry represents these repeated Ca-binding motifs.