G alpha (i) auto-inactivates by hydrolysing GTP to GDP

Stable Identifier
Reaction [transition]
Homo sapiens
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When a ligand activates a G protein-coupled receptor, it induces a conformational change in the receptor (a change in shape) that allows the receptor to function as a guanine nucleotide exchange factor (GEF), stimulating the exchange of GDP for GTP on the G alpha subunit. In the traditional view of heterotrimeric protein activation, this exchange triggers the dissociation of the now active G alpha subunit from the beta:gamma dimer, initiating downstream signalling events. The G alpha subunit has intrinsic GTPase activity and will eventually hydrolyze the attached GTP to GDP, allowing reassociation with G beta:gamma. Additional GTPase-activating proteins (GAPs) stimulate the GTPase activity of G alpha, leading to more rapid termination of the transduced signal. In some cases the downstream effector may have GAP activity, helping to deactivate the pathway. This is the case for phospholipase C beta, which possesses GAP activity within its C-terminal region (Kleuss et al. 1994).

Literature References
PubMed ID Title Journal Year
7937899 Mechanism of GTP hydrolysis by G-protein alpha subunits

Kleuss, C, Raw, AS, Lee, E, Sprang, SR, Gilman, AG

Proc Natl Acad Sci U S A 1994
Participant Of
Catalyst Activity
Catalyst Activity
GTPase activity of G alpha (i): GTP [plasma membrane]
Physical Entity
This event is regulated
Inferred From
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