Describe the steps of activation of GPCRs: A) Before a ligand (external signal t

Question

Describe the steps of activation of GPCRs: A) Before a ligand (external signal that activates the GPCR) binds, what state is the GPCR in? What state is the alpha subunit of the G-protein in? What state are the beta&gamma subunits of the G-protein in? B) When a ligand binds and activates the GPCR, what happens to the alpha subunit of the G- protein? What happens to the beta&gamma subunits? C) Using adenylyl cyclase as an example effector protein, what happens when the activated alpha subunit binds to adenylyl cyclase? What is the chemical reaction that is catalyzed by the adenylyl cyclase enzyme? What second messenger is made? How many molecules of the second messenger are made? Is there amplification at this step? D) What enzyme is activated by the second messenger you identified above? What does that enzyme do? Is there amplification at this step?
Describe the steps of activation of GPCRs: A) Before a ligand (external signal that activates the GPCR) binds, what state is the GPCR in? What state is the alpha subunit of the G-protein in? What state are the beta&gamma subunits of the G-protein in? B) When a ligand binds and activates the GPCR, what happens to the alpha subunit of the G- protein? What happens to the beta&gamma subunits? C) Using adenylyl cyclase as an example effector protein, what happens when the activated alpha subunit binds to adenylyl cyclase? What is the chemical reaction that is catalyzed by the adenylyl cyclase enzyme? What second messenger is made? How many molecules of the second messenger are made? Is there amplification at this step? D) What enzyme is activated by the second messenger you identified above? What does that enzyme do? Is there amplification at this step?
Describe the steps of activation of GPCRs: A) Before a ligand (external signal that activates the GPCR) binds, what state is the GPCR in? What state is the alpha subunit of the G-protein in? What state are the beta&gamma subunits of the G-protein in? B) When a ligand binds and activates the GPCR, what happens to the alpha subunit of the G- protein? What happens to the beta&gamma subunits? C) Using adenylyl cyclase as an example effector protein, what happens when the activated alpha subunit binds to adenylyl cyclase? What is the chemical reaction that is catalyzed by the adenylyl cyclase enzyme? What second messenger is made? How many molecules of the second messenger are made? Is there amplification at this step? D) What enzyme is activated by the second messenger you identified above? What does that enzyme do? Is there amplification at this step?

Explanation / Answer

Ans. Prior binding of ligand the GPCR remains bound to the heterdiatomic and is characterised by extracellular N terminus, seven transmembrane alpha helices and a C terminal. GPCR arranges itself with a tertiary structure and seven transmembrane cell providing the cavity for binding of the ligands. The beta site is for the phosphorylation after binding.

Ans. On binding of the ligand there would be numerous conformational change and as a result of which would finally result in the disorientation of the transmembrane helices. The binding would result in activation of GDP/GTP phosphorylation for the activity to proceed.

Ans. When an activated alpha subunit bounds to the adenyl cyclase there would be signal transduction and thus the signalling pathways activated through GPCR would be limited by the primary sequence and tertiary structure of the subunit. It is further proceeded by the cyclization of the ATP to cAMP which requires the cleavage of the pyrophosphate. It functions as a secondary messenger for signal transduction.

Ans. The enzyme protein kinase are activated by the second messenger. It would lead to the phosphorylation of the receptors.

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