Exploring allosteric coupling in the α-subunit of Heterotrimeric G proteins using evolutionary and ensemble-based approaches

We analyzed: 1) correlated mutations in the family of G protein α-subunits, and 2) cooperativity of the native state ensemble of the Gαi1 or transducin. The combination of these approaches not only recovered already-known details such as the switch regions that change conformation upon nucleotide exchange, and those regions that are involved in receptor, effector or Gβγ interactions (indicating that the predictions of the analyses can be viewed with a measure of confidence), but also predicted new sites that are potentially involved in allosteric communication in the Gα protein. A summary of the new sites found in the present analysis, which were not apparent in crystallographic data, is given along with known functional and structural information. Implications of the results are discussed.A set of residues and/or structural elements that are potentially involved in allosteric communication in Gα is presented. This information can be used as a guide to structural, spectroscopic, mutational, and theoretical studies on the allosteric network in Gα proteins, which will provide a better understanding of G protein-mediated signal transduction.G proteins and G protein-coupled receptors (GPCR) constitute a large family of signaling proteins that transmit extracellular signals to the intracellular milieu where the signals are integrated and transformed to a variety of biological responses. The receptor is activated by the binding of agonists, which are neurotransmitters, hormones, autacoids, odorants, taste or drug molecules present in the extracellular environment. The receptor then activates its cognate heterotrimeric G protein, which in turn transmits the signals to intracellular effectors, such as second-messenger generating enzymes or ion channels. The GDP-bound Gα subunit complexed with tightly bound Gβγ (i.e. the heterotrimer) is generally considered as the inactive state of the G protein. The agonist-activated receptor catalyses the release of bound-GDP from Gα and