Exotoxins Flashcards
C.diphtheriae
inhibits protein synth by inactivating EF-2
diphtheriae toxin
Pseudomonas aeruginosa
inhibits protein synth by inactivating EF-2 exotoxin A (attaches to ADP-ribosyl) [part of exotoxin AB, w/ B = binding component]
Shigella
Shiga toxin
inhibits protein synth by inactivating ribosome by removing ADENINE from rRNA
invades host cells!
EHEC (O157:H7)
Shiga-like toxin
inhibits protein synth by inactivating ribosome by removing ADENINE from rRNA
does NOT invade host cells!
ETEC
LT (heat labile) - overactivates ADENYLATE cyclase (increases cAMP) –> increase Cl secretion in gut + H2O efflux
ST (heat-STABILE) - overactivates GUANYLATE cyclase (increases cGMP) –> decreases resorption of NaCl and H2O in gut
B.anthracis
edema factor
MIMICS adenylate cyclase (increase cAMP)
V.cholerae
cholera toxin
overact. adenylate cyclase by PERMANENTLY ACTIVATING Gs –> increase Cl secretion in gut + H2O efflux
same Cl channel used in CFTR gene
B.pertussis
pertussis toxin
overact. adenylate cyclase by DISABLING Gi (increased sensitivity to histamine) and impairing phagocytosis!
C.tetani
tetanospasmin
prevent release of INHIBITORY NT (GABA, glycine) by cleaving SNARE protein
C.botulinum
botulinum toxin
prevent release of STIMULATORY NT at NMJ (ACh) by cleaving SNARE protein
C.perferingens
alpha toxin (lecithinase) phospholipase (DEGRAD OF PHOSPHOLIPASE C) that degrades tissue and cell membranes
enterotoxin - food poisoning
S.pyogenes
Streptolysin O
degrades cell membrane (causes RBC LYSIS)
Exotoxin A (superantigen) bind MHC II and TCR simultaneously --> POLYCLONAL expansion of T-cells --> overwhelming release of IFN-gamma and IL-2 --> shock!
S.aureus
TSST-1 (superantigen)
bind MHC II and TCR simultaneously –> POLYCLONAL expansion of T-cells –> overwhelming release of IFN-gamma and IL-2 –> shock!
exfoliative toxin - SSS
enterotoxin (preformed) - food poisoning
Yersinia toxin
increase cGMP by activating guanylate cyclase
