Visualizing the residues/domains that undergo significant electrostatic perturbation in the diphtheria toxin repressor (PDBid:1BI3).

<p>Threshold value above which perturbation are considered significant is 200 potential (difference) units. It can be seen that the C-terminal undergoes more electrostatic changes than the N-terminal. (a) Residues undergoing electrostatic perturbation of magnitude greater than the threshold value are colored in red and yellow (Met10). Met10 ligands metal ions, and its mutation to alanine results in complete inactivation of repressor activity. (b) Residues undergoing positive and negative electrostatic perturbations greater than the threshold value are colored in red and blue respectively. As expected, they are interspersed in order to maintain electrostatic homogeneity.