Regulation of effectors by G-protein α- and βγ-subunits: Recent insights from studies of the phospholipase C-β isoenzymes

Both the α- and βγ-subunits of heterotrimeric guanine nucleotide dependent regulatory proteins (G-proteins) couple members of the heptahelical class of cell-surface receptors to a diverse range of signal generating effectors including retinal cyclic GMP phosphodiesterase, ion channels, adenylylcyclases, phosphoinositide kinase, and members of the β-class of inositol lipid-specific phospholipases C. Although the molecular details of the G-protein-regulated phospholipase C system were elucidated comparatively recently, these enzymes have become an important model for investigations of the process of G protein effector coupling. A combination of molecular biological, biochemical, and structural studies using the phospholipase C-β enzymes has provided some important; insights into the interplay between G-proteins and their effecters and promises to reveal the mechanisms by which G protein α- and βγ-subunits selectively associate with and activate effecters.