Pertussis toxin inhibits which host-cell mechanism, leading to increased cAMP?

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Multiple Choice

Pertussis toxin inhibits which host-cell mechanism, leading to increased cAMP?

Explanation:
Pertussis toxin works by ADP-ribosylating the alpha subunit of the inhibitory G protein Gi. This modification prevents Gi from inhibiting adenylyl cyclase, so the enzyme stays active and produces more cAMP. The rise in cAMP is the result of removing Gi’s brake on adenylyl cyclase. If Gi were activated, cAMP would decrease; if adenylyl cyclase were inhibited, cAMP would also decrease; blocking calcium channels wouldn’t explain the increased cAMP.

Pertussis toxin works by ADP-ribosylating the alpha subunit of the inhibitory G protein Gi. This modification prevents Gi from inhibiting adenylyl cyclase, so the enzyme stays active and produces more cAMP. The rise in cAMP is the result of removing Gi’s brake on adenylyl cyclase. If Gi were activated, cAMP would decrease; if adenylyl cyclase were inhibited, cAMP would also decrease; blocking calcium channels wouldn’t explain the increased cAMP.

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