Figure 3. The influence of third-site mutations on allostery in CAP.
(A) Predicted influence of mutation of H160 on allostery in CAP. The chart represents the ratio of the second to first dissociation constants for cAMP (K 2/K 1) plotted against spring constant at H160 (k H160/k). The structure is the proposed corresponding mutation. (B) X-ray crystal structures for CAP showing the hydrogen bonding network at amino 160 in wild-type and H160L proteins. (C) ITC trace (upper panel) and binding isotherm (lower panel; the different coloured symbols represent individual experiments) for the calorimetric titration of cAMP to CAP H160L. The thermodynamic parameters obtained are shown in Tables 1 and S2.