GPCR-G alpha fusion proteins: molecular analysis of receptor-G-protein coupling

The efficiency of interactions between G-pratein-coupled receptors (GPCRs) and heterotrimeric guanine nucleotide-binding proteins (G proteins) is grea tly influenced by the absolute and relative densities of these proteins in the plasma membrane. The study of these interactions has been facilitated b y the use of GPCR-G alpha fusion proteins, which are formed by the fusion o f GPCR to Ga. These fusion proteins ensure a defined 1:1 stoichiometry of G PCR to GOL and force the physical proximity of the signalling partners. Thu s, fusion of GPCR to G alpha enhances coupling efficiency can be used to st udy aspects of receptor-G-protein coupling that could not otherwise be exam ined by co-expressing GPCRs and G proteins as separate proteins. The result s of studies that have made use of GPCR-G alpha fusion proteins will be dis cussed in this article, along with the strengths and limitations of this ap proach.