Fig. 5

Molecular modeling to fit the experimental SAXS curves of various DCs based on Scaf20L. a Left panel: experimental scattering curve of Scaf20L alone. The black line represents the best fit (mixture of extended and compact forms). Right panel: two structural models of scaffoldin Scaf20L that jointly fit the experimental SAXS data. The four domains of Scaf20L are indicated: the second cohesin of CipA from C. thermocellum (Coh2A), the third cohesin of ScaB from B. cellulosolvens (CohB3), the third cohesin of ScaC from A. cellulolyticus (CohC3) and the cellulose binding module of CipA from C. thermocellum (CBM3a). Note that none of the two structural models separately fits the experimental SAXS data. However, the two models taken together with equal statistical weights fit the SAXS data very well, see the black curve in a. b Left panel: experimental scattering curve of Scaf20L In complex with Cel8A-b. The black line represents the best fit obtained by the structural model presented in the right panel. Right panel: SAXS-derived structural model of the Scaf20L:Cel8A-b protein complex. Cellulase Cel8A-b is shown in orange, where its C. thermocellum catalytic domain (CD Cel8A) and B. cellulosolvens dockerin (Doc Cel8A) are labelled. The scaffoldin Scaf20L is shown in blue, with its cohesin and CBM modules labelled as in Fig. 5a. The disordered linkers adopt extended conformations. Note: a single Cel8A-b enzyme component interacts selectively via its B. cellulosolvens dockerin with the matching cohesin (CohB3) of Scaf20L and fails to interact with the other two non-matching cohesins. c Left panel: experimental scattering curve of Scaf20L in complex with 3 enzymes. The black line represents the best fit obtained by a single structural model presented in the right panel (χ² = 1.87). Right panel: detail of the SAXS-derived structural model of the Scaf20L-based complex with 3 enzymes. Scaffoldin Scaf20L is shown in blue, Cel48S-t in red, Cel9R-a in green, and Cel8A-b in orange. In this structure, the disordered linkers in Scaf20L adopt the most extended conformations. d Left panel: experimental scattering curve of Scaf20L in complex with 3 enzymes. The black line represents the best fit obtained by a mixture of the structural models presented in the right panel (χ² = 1.25). Right panel: two models of Scaf20L in complex with 3 enzymes. The color code is the same as in right panel of Fig. 5c. Neither of the two models separately fits the experimental SAXS data as well as the two models taken together with equal statistical weights