Prediction of functionally important residues based solely on the computed energetics of protein structure

Catalytic and other functionally important residues in proteins can often be mutated to yield more stable proteins. Many of these residues are charged residues that are located in electrostatically unfavorable environments. Here it is demonstrated that because continuum electrostatics methods can identify these destabilizing residues, the same methods can also be used to identify functionally important residues in otherwise uncharacterized proteins. To establish this point, detailed calculations are performed on six proteins for which good structural and mutational data are available from experiments. In all cases it is shown that functionally important residues known to be destabilizing experimentally are among the most destabilizing residues found in the calculations. A larger scale analysis performed on 216 different proteins demonstrates the existence of a general relationship between the calculated electrostatic energy of a charged residue and its degree of evolutionary conservation. This relationship becomes obscured when electrostatic energies are calculated using Coulomb's law instead of the more complete continuum electrostatics method. Finally, in a first predictive application of the method, calculations are performed on three proteins whose structures have recently been reported by a structural genomics consortium.