Fig. 3. Superpositions of the backbones of 20 low energy structures of SmpB. Structures shown are equally consistent with the NMR data, color-ramped from blue near the N-terminal to red near the C-terminus of the protein. The 20 models are a fair representation of the full range of structures that are consistent with the NMR-derived constraints and reasonable molecular geometry. (A) Superposition of the 20 models was performed by minimizing the differences in the coordinates of the backbone atoms of residues 6–128. Residues 1–133 of the protein are shown. (B) The 20 structures were superimposed by minimizing the differences in the coordinates of the backbone atoms within the six strands of the β-barrel; only the residues of these six β-strands are shown.