Question

A G protein has a Gα subunit that is incapable of GTP hydrolysis. How will this impact the GPCR?____

a. The α subunit will be incapable of binding to the Gβ and Gγ subunits.
b. The GPCR will be unable to bind ligand.
c. The α subunit will not dissociate from the GPCR.
d. The Gβ and Gγ subunits will not interact.
e. None of the answers is correct.

Answer 1

c. The α subunit will not dissociate from the GPCR.

Step-by-step explanation:

When a G protein has a Gα subunit that is incapable of GTP hydrolysis, it means that the α subunit cannot convert GTP to GDP, leading to a persistent active state. In the normal G protein cycle, GTP hydrolysis is crucial for terminating the signaling cascade. The Gα subunit with impaired GTP hydrolysis remains bound to GTP, preventing its dissociation from the GPCR.

This prolonged association maintains the activation of the downstream signaling pathway. Consequently, the correct response is option c: "The α subunit will not dissociate from the GPCR." This condition disrupts the usual regulatory mechanism and sustains the signaling process, potentially leading to aberrant cellular responses. The other options (a, b, d, and e) do not accurately reflect the impact of a Gα subunit incapable of GTP hydrolysis on the GPCR signaling pathway.