Northern blot of G protein β subunit expression. Total mRNA (20 μg) isolated from untransfected C₂D₇ cells (as control, C) and cells transfected with different G protein β subunits (as marked) were hybridized with subunit-specific oligonucleotide probes (see Materials and Methods). Positions of the RNA size standards (in kilobases) are shown on the left. Heterologously expressed Gβ subunits are marked with an arrow on theright. Endogenous Gβ subunits were expected to have similar sizes. However, because they were expressed in much lower amounts, they would not be detected under these experimental conditions.