Figure 6
(a) Box and whisker plots of L. lactis strains binding to Fg as determined by AFM. Whisker ends 9th and 91st percentiles. Box ends 25th and 75th percentiles. Median is marked with horizontal line. Blue- or red-colored boxes represent median force values that are, respectively, less than or greater than the wild type strain (L. lactis A). P-values calculated using Mann-Whitney, where p < 0.001 is indicated by ***. (b) Histogram representation of the binding forces shown in panel (a). One group of binding forces at ~200 pN is observed in all of the strains. A second set of higher binding forces (~1.3 nN) is present only in the E652D/H782Q variant. (c) Dependence of binding or dissociation force (f; pN) on the logarithm of the loading rate, (r; pN s−1) between Fg and FnBPA expressed on the surface of the L. lactis E652D/H782Q. Different force-loading regimes (shown as different colors) are indicative of multiple binding pathways. AFM measurements were conducted in PBS at retraction velocities from 0.05 to 18.8 µm/s. AFM tips were coated with protein by incubating tips in 100 µg/mL of Fn or Fg prior to force measurements.
