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Lecture - Cell Communication and Energy Oct 16

G protein is inacve when guanosine diphosphate

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Unformatted text preview: s to the binding site •  binding causes conforma<onal change of the receptor C terminus •  conforma<onal change ini<ates cascade of events G protein-coupled receptor •  G protein coupled receptor interacts with G protein •  G- protein is aMached to the cytoplasmic side of the plasma membrane. •  G- protein is inac<ve when guanosine diphosphate (GDP) is bound. G protein Activation •  When the ligand binds to the receptor, the receptor undergoes a conforma<onal change (it changes shape) and is considered ac<vated. The G protein binds to the receptor and the GDP on the G protein is displaced by GTP (guanosine triphosphate). Binding of the GTP ac<vates the G protein. Other signal transduc2on events •  The ac<vated G protein dissociates from the G protein- coupled receptor and travels along the cytoplasmic side of the membrane towards a membrane bound enzyme. •  Ac<vated G protein binds to the membrane bound enzyme and ac<vates it. Other signal transduc2on events •  The ac<vated enzyme goes on to catalyze other signal transduc<on events. G protein Inactivation •  Following enzyme ac<va<on, the GTP is hydrolyzed to GDP (phosphate is removed by hydrolysis). The inac<ve G protein (inac<ve because a GDP is now aMached) returns to it’s star<ng posi<on near the G protein- coupled receptor. •  The system is now ready to be re- ac<vated. G protein-coupled receptor...
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