Question

What causes the inactivation of a G protein?

Please choose the correct answer from the following choices, and then select the submit answer button.


-The alpha subunit catalyzes the hydrolysis of GTP to GDP and inorganic phosphate.

-The inactive receptor catalyzes the replacement of GTP by GDP.

-A phosphatase removes the inorganic phosphate group from GTP.

-The beta and gamma subunits trigger the hydrolysis of GTP to GDP.

Answer 1

Final answer:

The inactivation of a G protein is caused by the hydrolysis of GTP to GDP catalyzed by its alpha subunit, after which the inactivated subunits reassociate.

Step-by-step explanation:

The inactivation of a G protein occurs when the alpha (α) subunit catalyzes the hydrolysis of guanosine triphosphate (GTP) to guanosine diphosphate (GDP) and inorganic phosphate. This enzymatic activity transforms the GTP-bound active form of the G protein α subunit back to its inactive GDP-bound form.

Following this, the α subunit reassociates with the beta (β) and gamma (γ) subunits, reforming the inactive G protein complex, ready to be activated again by a G-protein-coupled receptor (GPCR).Once the G protein is activated by binding to the receptor and exchanging GDP for GTP, the GTP on the active alpha subunit is hydrolyzed to GDP. This leads to the deactivation of the G protein.