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).
Wenzel-Seifert, K, Liu, HY, Seifert, R
Baker, LP, Nielsen, MD, Impey, S, Metcalf, MA, Poser, SW, Chan, G, Obrietan, K, Hamblin, MW, Storm, DR
Kozasa, T, Itoh, H, Tsukamoto, T, Kaziro, Y
Zhang, JY, Nawoschik, S, Kowal, D, Smith, D, Spangler, T, Ochalski, R, Schechter, L, Dunlop, J
Mitsuhashi, M, Mitsuhashi, T, Payan, DG
guanyl-nucleotide exchange factor activity of Ligand:GPCR complexes that activate Gs:Heterotrimeric G-protein Gs (inactive) [plasma membrane]
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