Figure 4.

Histogram comparison of the electrostatic potential Φ_el,i at the positions of catalytically important atoms for N-protonation. The value of Φ_el,i was calculated in each case at grid points coinciding with the position of the catalytically important atom of the residue, i.e., N(1), C(7), O(8), O^γ(S70) (=S70′), N(S70) (=S70′′), N^ɛ(K73), O^γ(S130), O^ɛ1,2(E166), N^ɛ(K234), N(A237), and O(WAT297). The value for O^ɛ1,2(E166) is given at the grid point midway between the two carboxylate oxygens. Although the N(1), C(7), and O(8) atoms do not occur in the free enzyme E, the values of Φ_el,i are given at the grid points that are occupied by these atoms in the ES complex.