Regulates G protein-coupled receptor signaling cascades. Inhibits signal transduction by increasing the GTPase activity of G protein alpha subunits, thereby driving them into their inactive GDP-bound form. The RGS6/GNB5 dimer enhances GNAO1 GTPase activity. Interacts with GNB5 (By similarity). Interacts with RGS7BP, leading to regulate the subcellular location of the heterodimer formed with GNB5 (By similarity). Interacts with GNAI1 (By similarity). Interaction with GNB5 mediates translocation to the nucleus. The RGS domain interacts avidly with Galpha and mediates the acceleration of Galpha-mediated GTP hydrolysis.