[Campbell Biology P.267] A bacterial toxin is known to interfere with G protein function by ... | Practice Question

A bacterial toxin is known to interfere with G protein function by inhibiting its intrinsic GTPase activity. Based on the information provided, what would be the most likely consequence of such a toxin on cellular signaling?

  • A: The G protein would remain permanently active, leading to continuous activation of the enzyme and an exaggerated cellular response.
  • B: The G protein would be unable to bind to the receptor, preventing the initiation of signaling.
  • C: The G protein would remain permanently inactive, unable to bind to GTP.
  • D: The signaling pathway would shut down rapidly even when the signaling molecule is present.

Explanation

The text states that the G protein's GTPase function allows the pathway to shut down rapidly by hydrolyzing GTP to GDP, returning the G protein to its inactive state. If this activity is inhibited, the G protein would remain bound to GTP and thus remain permanently active, continuously signaling to the enzyme and leading to an exaggerated or prolonged cellular response.