FIGURE 1.

Overview of the cellulosome and the cohesin-dockerin complex in C. thermocellum. A, scheme of the cellulosome organization. The primary scaffoldin (yellow) contains nine type I cohesin modules (CohI), a single cellulose-specific CBM, and a type II dockerin module (XDocII). Each type I cohesin binds a type I dockerin module (DocI). This module occurs in a variety of cellulases and other carbohydrate-active enzymes (shades of blue and green). The primary scaffoldin (yellow) is attached to one of several cell-anchoring scaffolds via interaction between type II dockerin (XDocII) and type II cohesin (CohII). The anchoring scaffoldins (pale orange) contain type II cohesin modules and a surface layer homology (SLH) module that is connected to the cell surface. B, structure of the type I cohesin-dockerin interface (cohesin, red; dockerin, blue; Protein Data Bank code 1OHZ (12)). The hydrophobic patch at the interface is shown in spheres; the residues involved in the hydrogen bond network are depicted as sticks (atoms in this and subsequent figures are colored in Corey-Pauling-Koltun). C and D, sequence conservation at the cohesin-dockerin interface. The hydrophobic patch at the cohesin-dockerin interface is conserved across species (C). In contrast, the network of hydrogen bonds is conserved within C. thermocellum (Ct) but replaced by hydrophobic residues in C. cellulolyticum (Cc) cohesin-dockerin interfaces (D). Multiple sequence alignments are shown for different cohesin repeats (red) and dockerins from different enzymes from C. thermocellum and C. cellulolyticum (blue). The dual binding mode is shown in cartoon representation. The first dockerin segment is colored dark blue and the second is colored light blue; calcium ions are shown as green spheres.