Figure 5. CsgC binds curli and halts curli elongation.

(a) Normalized ThT fluorescence of an 8 µM CsgA solution supplemented with 1000:1, 500:1, 100:1, 1:1 CsgC respectively (from dark to light grey); (b) apparent hydrodynamic radii of CsgA as a function of time for a 14 µM CsgA solution (circles), supplemented with 100:1 CsgC at t=0 h (t0; triangles) and at tx=3 h (diamonds) determined using dynamic light scattering (as a guide, dashed lines give apparent rates of fiber growth with CsgC added at 0 $\left(r_{t0}^C\right)$ or 3 hours $\left(r_{tx}^C\right))$; (c) mean fiber length determined using TEM after 3.5 min incubation in an 8 µM CsgA solution alone (CsgA), or supplemented with 100:1 CsgC (+CsgC) (n=150); (d, e) elongation of single fibers as a function of time in a 90 nM CsgA solution alone (d) or supplemented with 10:1 CsgC (e); (f) Immuno-fluorescence microscopy demonstrating binding of CsgC to matured CsgA fibrils: brightfield view, CsgsA-His in the fibers (α-His) and bound CsgC-strep (α-Strep).