G alpha (i)1 auto-inactivates by hydrolysing GTP to GDP

Stable Identifier
R-RNO-421896
Type
Reaction
Species
Rattus norvegicus
Compartment
Summation

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 Proc Natl Acad Sci U S A 1994
Participants
Catalyst Activity
Catalyst Activity
Title
GTPase activity of Guanine nucleotide-binding protein G(i), alpha-1 subunit [plasma membrane]
Physical Entity
Activity
Orthologous Events