Figure 6. Free-energy sampling of the conformational mobility of FHT domains interacting with five-mer filaments.

(A) Two independent metabasin metadynamics (MBMetaD) simulations for each formin were carried out (run for 80 ns) to understand the conformational mobility of the FHT domain. The collective variables (CVs) defined in (B) were selected to describe the mobility of the FHT domain in the region of the incoming actin subunit A1 (shown by dashed black lines). The first CV (CV1) is the distance between the center of mass (COM) of FHT knob and the COM of actin subunit A2. CV2 is the distance between the COM of the FHT post and the COM of actin subunit A2. Initial distances from the knob and post to the COM of A2 are marked with ‘X’. If a larger area was favored to be explored, that would mean that the incoming actin monomer could be more easily accommodated into the barbed end as the rearrangement of the FHT domain requires a lower energy barrier. (B) Space-filling models of the barbed end of the filament (subunit A2 is yellow and subunit A3 is brown) and ribbon diagrams of the FH2 domains of Cdc12 (green with the knob and post of FHT in purple). (C) The distributions of angles between actin subunits A2 and A3 during two independent MBMetaD simulations.