Mammalian regulators of G-protein signalling also contain these domains, and regulate signal transduction by increasing the GTPase activity of G-protein alpha subunits, thereby driving them into their inactive GDP-bound form. It has been proposed that the DEP domain could play a selective role in targeting DEP domain-containing proteins to specific subcellular membranous sites, perhaps even to specific G protein-coupled signaling pathways.[2][3]Nuclear magnetic resonance spectroscopy has revealed that the DEP domain comprises a three-helix bundle, a beta-hairpin 'arm' composed of two beta-strands and two short beta-strands in the C-terminal region.[3]