Figure 4. Point mutations modulate flux between pathways.

Comparison of the force dependence of the unfolding rates (s⁻¹) of src SH3 variants in the shearing geometry, obtained from force-jump experiments. The kinetics were recorded for at least six individual tethers, and the data shown were obtained from one such tether. Each tether was analysed separately, and there was very little variation in rates between the tethers. Some point mutations affect both pathways similarly (a), while others affect the two pathways differentially by lowering the barrier height of primarily either S1 (b) or S2 (c). The location of the point mutations in the protein is shown in the inset.