Figure 3
Urea denaturation curves for human profilin I and the three mutants that have strongly reduced PI(4,5)-P2 binding. For each profilin the ratio of the intrinsic fluorescence (F) at two different wavelengths F(352 nm)/F(332 nm) is plotted versus the urea concentration. Wild type profilin I (closed squares), R136D (open circles), R88A/R136D (open triangles), R88E/R136D (closed circles). The inserted table lists the urea concentration at the midpoint of the fluorescence transition. These values are a measure for the stability of the proteins.