The liganded receptor undergoes a conformational change, generating a signal that is propagated in a manner that is not completely understood to the the G-protein. This stimulates the exchange of GDP for GTP in the G-protein alpha subunit, activating the G-protein. This event is negatively regulated by some Activators of G protein signaling (AGS) proteins, a class of proteins identified in yeast functional screens for proteins able to activate G protein signaling in the absence of a G protein–coupled receptor (GPCR) (Cismowski et al. 1999, Takesono et al. 1999). AGS proteins contain G protein regulatory (GPR) motifs (also referred to as the GoLoco motif) that bind and stabilize the Galpha subunit in its GDP-bound conformation (Mochizuki et al. 1996, Peterson et al. 2000, Cao et al. 2004, Blumer & Lanier 2014). Some RGS proteins similarly bind to Galpha preventing the exchange of GDP for GTP (Soundararajan et al. 2008).
Baker, LP, Metcalf, MA, Obrietan, K, Storm, DR, Impey, S, Chan, G, Poser, SW, Nielsen, MD, Hamblin, MW
Liu, HY, Seifert, R, Wenzel-Seifert, K
Itoh, H, Tsukamoto, T, Kozasa, T, Kaziro, Y
Dunlop, J, Schechter, L, Smith, D, Zhang, JY, Spangler, T, Kowal, D, Ochalski, R, Nawoschik, S
Mitsuhashi, M, Mitsuhashi, T, Payan, DG
guanyl-nucleotide exchange factor activity of Ade-Rib:ADORA2B:Heterotrimeric G-protein Gs:GDP [plasma membrane]
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