Peussis toxin acts by all of the following mechanisms, EXCEPT:
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.
ADP ribosylation of proteins associated with receptors
Increase cyclic AMP
Increased calcium release from sarcoplasmic reticulum
Acts through G alpha subunit