Fig. S5.
Stoichiometry of FtsKC approaching unsynapsed dif. During FRET, the Cy5 attached to FtsKC must be within ∼10 nm of the Cy3B attached to the DNA; hence, we know where in the evanescent field the Cy5 is (on average). (Right) Corrected intensity during FRET events for unsynapsed DNA conformations was extracted and histogrammed (n = 122). (Left) Given a labeling efficiency of 53%, a correction for the distance along the DNA in our evanescent excitation field, and the width of the intensity distribution for single Cy5-FtsK pulled down to the surface, we plot the predicted intensity distribution for a single hexamer (red) and a double hexamer (blue) of FtsKC. We find that a single hexamer provides a better explanation of our data [sum of squared deviation (SSD) = 230 for the single hexamer and SSD = 600 for the double hexamer].