G-protein coupled receptors catalyze nucleotide exchange on G proteins, which results in subunit dissociation and effector activation. In the recent beta(2)AR-G(s) structure, portions of Switch I and II of G alpha, are not fully elucidated. We paired fluorescence studies of receptor-G alpha(i) interactions with the beta(2)AR-G(s) and other G(i) structures to investigate changes in Switch I and II during receptor activation and GTP binding. The beta 2/beta 3 loop containing Leu194 of G alpha(i) is located between Switches I and II, in close proximity to IC2 of the receptor and the C-terminus of G alpha, thus providing an allosteric connection between these Switches and receptor activation. We compared the environment of residues in myristoylated G alpha(i) proteins in the heterotrimer to that upon receptor activation and subsequent GTP binding. Upon receptor activation, residues in both Switch regions are less solvent-exposed, as compared to the heterotrimer. Upon GTP gamma S binding, the environment of several residues in Switch I resemble the receptor-bound state, while Switch II residues display effects on their environment which are consistent with their role in GTP binding and G beta gamma dissociation. The ability to merge available crystal structures with solution studies is a powerful tool to gain insight into conformational changes associated with receptor-mediated G(i) protein activation. (c) 2013 Elsevier Inc. All rights reserved.