(A) Structure of the BoNT/A LC catalytic domain in ribbon representation. The catalytic binding site with Zn located at the center (red), the α-exosite (yellow), the β-exosite sheet (magenta), the anchor site and other loops surrounding these binding sites are shown. (B) Calculated B-factors from MD simulations in comparison with the experimental B-factors. (C) Conformations of BoNT/A observed from essential dynamic analysis. The first essential mode is associated with loops 200, 250, and 370 at the β-exosite, while the second dynamical mode is found with loops 60 and 170 surrounding the active site.