G protein–coupled receptors (GPCRs) are key signaling proteins that regulate nearly every
aspect of cell function. Studies of GPCRs have benefited greatly from the development of
molecular tools to monitor receptor activation and downstream signaling. Here, we show that
mini G proteins are robust probes that can be used in a variety of assay formats to report
GPCR activity in living cells. Mini G (mG) proteins are engineered GTPase domains of Gα
subunits that were developed for structural studies of active-state GPCRs. Confocal imaging …