Mechanical mechanism for the translocation of hexameric and nonstructural helicases: Dependence on physical parameters.

Three recently observed facts of the translocation of actual hexameric and nonstructural (NS) helicases are related to the various physical quantities and are in accordance with the recently proposed mechanical mechanism: a) the translocation of hexameric helicases might be led by either the N-terminal domain (NTD) or C-terminal domain (CTD) depending on which domain has a smaller central pore, b) the translocation speed (vt) of the ring-shaped helicases and NS helicases decreased with decreasing applied tension, and c) a large difference in the vt of the NS helicase was observed for the helicase translocating on DNA and RNA. These findings are the effects of the physical quantities of the helicase/nuclei acid strands on the translocation of helicases and are difficult to explain with biochemical models. We predict that a similar behavior as described in b) and c) is also shown by hexameric helicases. The validity of the mechanical mechanism is demonstrated in simulation experiments.