This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Peusis toxin acts by all of the followingmechanisms except ? 
Select and explain. 
A. ADP ribosylation of proteins associated with receptors, B. Increase cyclic AMP, C. Increased calcium release from sarcoplasmic reticulum, D. Acts through G alpha subunit
C: Increased calcium release from sarcoplasmic reticulum
Answer: C: Increased calcium release from sarcoplasmic reticulum 
Explanation: Increased calcium release from sarcoplasmic reticulum IRef: Harrison 170i/e p. 933] Peussis toxin is an exotoxin that has A and B subunits. B subunit binds to the target cells whereas A subunit acts on the target. First, the peussis toxin itself gets activated by glutathione and ATP. Once the toxin gets activated it activates cell membrane bound G proteins. Peussis toxin catalyzes the ADP ribosylation of the G proteins and activates them. The activated G protein in turn activates adenylate cyclase, this results in an outpouring of cAMP which activates protein kinase and other intracellular messangers. Peussis toxin 1 Gets activated by glutathione and ATP Activated peussis toxin Catalyses ADP ribosylation of G proteins Activated G proteins Activates adenylate cyclase Increased outpouring of cAMP