Question

The G-protein-coupled receptors are a diverse family with this common feature?

1) They are activated when a kinase molecule phosphorylates them.
2) They are activated when GTP is released from the G protein.
3) They are activated when GTP binds to the G protein.
4) They are activated when the α subunit binds to the β and γ subunits.

Answer 1

G-protein-coupled receptors are activated when GTP binds to the G protein, causing the G protein to release GDP and undergo subunit dissociation, leading to activation of other cellular proteins.

Step-by-step explanation:

The common feature of G-protein-coupled receptors (GPCRs) is that they are activated when GTP binds to the G protein. This process begins when a ligand binds to a GPCR, causing a confirmational change that allows the G protein bound to the receptor to release GDP and pick up GTP.

As a result of GTP binding, the active G protein splits into the alpha (α) and beta-gamma (βγ) subunits, which can then activate other proteins within the cell. This leads to a variety of cellular responses, depending on the type of GPCR and tissue involved. Eventually, GTP is hydrolyzed back to GDP, causing the α and βγ subunits to reassemble into the inactive G protein, ready to start the cycle over.