Figure 5.

Proposed model for PfD inhibition by 8-NBD-cGMP and comparison of calculated versus measured kinase activities. A, inhibition occurs through a three-state equilibrium, sampling a distinct holo-inactive intermediate state, where the pre-lid and PBC are engaged, similarly to the active state, but the lid is disengaged, similarly to the inactive state. The population of each state (P) is indicated. The structural shifts of the αB and αC helices are indicated with black arrows. The β-barrel is indicated with a rectangular box. The yellow starburst indicates the steric clash between the 8-NBD substituent and the Arg⁵²⁸ side chain. B, correlation plot of experimental versus predicted relative kinase activities. The kinase activity prediction is based on the populations of inactive, intermediate, and active states (Table S1). Error bars for the experimental kinase activity represent the standard deviation of multiple measurements, and for the predicted kinase activity represent the errors propagated from the errors on the populations, which are determined from the standard deviation of the fractional shift (X) values of the residues used to calculate the average X values.