Fig. 2.

RuvAB-catalyzed migration of single Holliday junctions. The contour length of cruciform arms tethering beads to a surface is plotted as a function of time for four values of the applied force. (A and B) Episodes of branch-migration activity are interrupted by pauses (arrows). Branch migration changes direction after a pause (as illustrated in A) in ≈50% of cases. (C) Branch-migration episode illustrating forward motion, in which the height of the bead decreases, against the applied force. (D) Reverse branch-migration event in which the applied force and the RuvAB complex promote branch migration in the same direction. Changes in branch-migration rate are observed in both forward and reverse motion (as illustrated in B and C). The data were fitted with piecewise linear functions by using the Levenberg–Marquardt algorithm.