For protein pK a calculations a program from OpenEye based on the Zap finite difference PB solver was used. For the partial charges of the protein, Delphi radii and CHARMM36 all-hydrogen partial charges were used, and the am1bccsym method was used to assign appropriate charges to the benzoic acid. The benzoic acid fragment outside the hinge was removed from the structure. The pK a of the ligand's carboxylic group was set to 4.2 according to the experimental value. An inner dielectric of 15, an ionic strength of 0.05 M, and an ionization (i.e., pH) of 6.9 were used.