Figure 2. The N-terminal region BR_120–186 forms a non-globular, flexible structure as revealed by SAXS.

(A,B) Processed solution scattering data (black dots) from (A) BR_187–385 and (B) BR*_120–395 fit to the theoretical scattering curves (red lines) from ensembles of 50 monomer models obtained from the ensemble optimization method (EOM) with χ-values of 0.9 and 1.7. (C,D) The histograms of the radii of gyration distribution of the pool of 10 000 structures generated by EOM (dotted lines) and the R_g distribution of the selected ensembles (solid lines). (C) The ensemble of 50 BR_187–385 molecules selected by EOM was separated into two groups. The first group had an R_g value of around 20 Å and is represented by the molecular model with the extension colored in cyan. The second had an extended R_g value of 22.5 Å and is represented by the molecular model with the extension colored in blue. (D) The ensemble of 50 BR*_120–395 molecules had a similar distribution of R_g values as compared the large pool of molecules with random conformations of the extensions. The two illustrated models displayed in blue and cyan have R_g values of 52 and 26 Å, respectively.