Peussis toxin acts by all of the following mechanisms, EXCEPT:
Correct Answer: Increased calcium release from sarcoplasmic reticulum
Description: Peussis toxin is the major virulence factor of B.peussis. It is an A-B toxin produced from a single operon as an enzymatic subunit & 5 binding subunits that are assembled into the complete toxin on the bacterial surface. B subunit binds to the target cells whereas A subunit acts on the target. The binding subunits mediate attachment of the toxin to the carbohydrate moieties on the host cell surface. The enzymatic subunit is then internalised & ADP- ribosylates a G protein that affects adenylate Cyclase activity. Unlike cholera toxin, which in essence keep cyclase activity turned on peussis toxin freezes the opposite side of the regulatory circuit & cripples the capacity of the host cell to inactivate cyclase activity. Multiple Intracellular signalling pathways are disrupted by this G protein modification. Among the results of this action are lymphocytosis, insulinemia & histamine sensitisation. Ref: Ray C.G., Ryan K.J. (2010). Chapter 31. Haemophilus and Bordetella. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.
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