Small angle X-ray scattering reconstruction of NBD1 and NBD2. Ab initio models of NBDs were determined from experimental SAXS data under different point-group symmetries using DAMMIN. The fits for NBD1 (A) and NBD2 (E) under different symmetry conditions are displayed as a function of normalized spatial discrepancy (NSD), discrepancy between the calculated and experimental SAXS curves (χ2), and standard errors (SE) of χ2. Sixteen independent runs were performed using P1, P2, P4, P8 and P222 symmetry. Ensemble average and respective fits for NBD1 (B and C) and NBD2 (E and F) based on P222 symmetry.