In cholera, there is uncontrolled secretion of sodium ions and water into the intestinal lumen because of the action of cholera toxin on a G protein coupled receptor system. How does the toxin act?

M.Sc. Bio-Chemistry (PU-CET P.G) 2017 Panjab University Entrance Exam With Answers

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67.

A: Cholera toxin activates a Gi (inhibitory) protein.

B: Cholera toxin inhibits phosphodiesterase so that the signal is not switched off.

C: Cholera toxin inhibits the binding of vasoactive intestinal polypeptide to the receptor.

D: Cholera toxin inhibits the GTPase activity of the G protein alpha subunit.

The answer is: D

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