Local electrostatic optimization in proteins

A simple electrostatic model has been used to investigate the extent to which the structure of protein molecules is organized to optimize the internal electrostatic interactions. We find that the model provides a favorable total intra-protein electrostatic energy for almost all polar and charged groups of atoms, suggesting a high degree of structural optimization. By contrast, a significant fraction of individual group-group interactions are found to be unfavorable. An analysis as a function of the range of interactions included shows the electrostatic organization is generally relatively short range (up to 6 or 7 Angstrom between group centers). Although the model is very simple, it is useful for assessing the overall quality of protein experimental structures, for pin-pointing some types of errors and as a guide to improving protein design.