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. Author manuscript; available in PMC: 2007 Sep 25.
Published in final edited form as: Biochim Biophys Acta. 2006 Dec 15;1768(4):772–793. doi: 10.1016/j.bbamem.2006.12.002

Fig. 1.

Fig. 1

Signal transduction of hormone binding to receptor into activation of adenylyl cyclase by the Gs G protein as understood in 1983. Gs is shown to undergo a GTP–GDP driven subunit dissociation–reassociation cycle, in which the role of the receptor is to keep the system cycling by promoting the Mg2+-induced exchange of GTP for GDP and in which the role of GTPα is both the activation of the enzyme and its own time-limited inactivation that comes about when it hydrolyzes GTP to GDP. (Adapted from Hildebrandt et al., 1984a [119]).