FIG. 7.

Schematic overview of the proposed cellulosome system in R. flavefaciens strain 17. The system is characterized by at least four different cohesin-dockerin specificities, designated a to d. (a) The conserved XDoc dyad of CttA, like that of ScaB, interacts with the ScaE cohesin. (b) The seven ScaB cohesins interact with the ScaA dockerin, thereby increasing the number of components that are incorporated into the R. flavefaciens cellulosome. (c) The ScaA cohesins bind either directly to a group of dockerin-containing enzymes (Cel44A-like) or to the dockerin of ScaC, whose divergent cohesin recognizes and incorporates into the cellulosome a different set of dockerin-containing enzymes and other components (d).