Prediction and confirmation of a site critical for effector regulation of RGS domain activity.

A critical challenge of structural genomics is to extract functional information from protein structures. We present an example of how this may be accomplished using the Evolutionary Trace (ET) method in the context of the regulators of G protein signaling (RGS) family. We have previously applied ET to the RGS family and identified a novel, evolutionarily privileged site on the RGS domain as important for regulating RGS activity. Here we confirm through targeted mutagenesis of RGS7 that these ET-identified residues are critical for RGS domain regulation and are likely to function as global determinants of RGS function. We also discuss how the recent structure of the complex of RGS9, Gt/i1alpha-GDP-AlF4- and the effector subunit PDEgamma confirms their contact with the effector-G protein interface, forming a structural pathway that communicates from the effector-contacting surface of the G protein and RGS catalytic core domain to the catalytic interface between Galpha and RGS. These results demonstrate the effectiveness of ET for identifying binding sites and efficiently focusing mutational studies on their key residues, thereby linking raw sequence and structure data to functional information.