Interaction of alpha2-Adrenergic Receptors With G-Proteins

A wide variety of hormones and neurotransmitters have been shown to produce intracellular signals mediated by guanine-nucleotide binding proteins (G-proteins). These have been shown to form a link between receptors on the extracellular face of the cell membrane, and their intracellular second-message-generating effectors, such as phospholipase C and adenylyl cyclase. An increasing number of different heterotrimeric G-proteins have been isolated, with varying degrees (50-95%) of sequence homology. This similarity of sequence has raised questions of specificity of interaction of G-proteins: do individual G-proteins interact only with specific receptors and effectors, or are they more promiscuous in their interaction? This question has been addressed by examining the specificity of coupling of G-proteins to alpha2-adrenergic receptors in two model systems