Fig. 4.

Cartoon representation of the DNA translocation mechanism viewed from the C-terminal side (beneath the staircase). The subunits are colored as in Fig. 2 with individual DNA nucleotides represented as beads on a string in a variable gradient shade of cyan. For each transition, the arrow color indicates the subunit moving from the bottom of the staircase to the top. Each subunit passes sequentially through the full complement of DNA-binding and ATPase states with its two DNA-binding hairpins escorting two nucleotides of ssDNA through the central channel (see Supplementary Movie 2)