Fig. 2: ATP hydrolysis triggers coordinated C-tier rotations and DNA translocation.

a, Overlay of initial (frame 1) and final (frame 5) states from the first variability component, showing the magnitude and direction of C-tier rotations in each subunit. b, Overlay of DNA conformations and DNA-binding residues K512 and/or H513 across the trajectory, demonstrating coordinated movements. c, Side-by-side comparison of initial and final DNA states, including H513 interactions. Nucleotides are coloured by associated subunit; hydrogen bonds are shown as red dotted lines. Green arrows indicate backbone phosphate bound to the loop of subunit D, highlighting the net translocation of one base along the trajectory. d, Superposition of subunit B from initial and final frames of the trajectory showing C-tier rotation, resulting in a downward shift of both the DNA-binding loop and bound DNA. e, Top, interactions at nucleotide-binding pocket between subunits B and C in the initial and final frames. The calculated BSA is shown, alongside the assigned interface type. Hydrogen bonds are shown as black dotted lines. The analysis shows disruption at the BC interface, indicating a catalytic event at the hydrolysis site. Middle, map density around nucleotide and DNA. Bottom, cryo-EM maps without postprocessing, depicting the helicase channel region, showing weak but persistent density for the passive strand at the DNA nexus. f, Atomic models coloured by B factor, showing increased overall mobility in the final state.