Does the ternary complex act as a secondary proton pump and a GTP synthase?

It has been suggested that G protein-coupled receptors can act as proton transporters, with the activated G protein-coupled receptor transporting H+ across the membrane from the extracellular side to the cytoplasm. In this article, Paul Nederkoorn, Henk Timmerman and Gabriëlle Donné-Op den Kelder summarize the various H+ translocation mechanisms and how these compare with activated G protein-coupled receptors. The G protein, being part of the ternary complex, is proposed to use translocated protons to synthesize GTP from GDP and Pi, thus functioning in a similar manner to ATP synthase. The importance of these events in physiological effects such as signal amplification is discussed.