Specificity of the cohesin-borne scaffoldin for its matching dockerins (a) and of the dockerin-bearing enzymes for their target cohesins (b-d). The interaction between scaffoldin 19L (Scaf19L) and its matching dockerins was examined (a) using a standardized matching fusion-protein system . Scaf19L was coated onto the wells of a microtiter plate and was subjected to interaction with Xyn-Doc fusion proteins, Xyn-Doc t (red), Xyn-Doc a (blue), Xyn-Doc b (green), and a non-matching control Xyn-Doc f, the divergent dockerin of which was derived from a cellulosomal component of the rumen bacterium, Ruminococcus flavefaciens (black). Anti-xylanase antibodies were used, together with a second antibody-conjugated enzyme system to promote a chromogenic reaction. Similarly, the interaction between the enzymes via their dockerin module to matching and non-matching cohesins was examined. In this case, 9K-a (b), 48S-t (c) and 8A-b (d), which bear an A. cellulolyticus, C. thermocellum and B. cellulosolvens dockerin, respectively, were coated onto the wells of microtiter plates and subjected to interaction with the designated carbohydrate binding module (CBM)-fused cohesin modules, Coh T (red), Coh A (blue) and Coh B (green).