methods of secretion
DESCRIPTION
Methods of Secretion. Protein Secretion. Type II Secretion (GEP). Sec dependent Signal peptide Chaperone 2 Stage E.gIgA-protease, Pertussis toxin, Serratia haemolysin. General Secretion Pathway (Type II). Type II:Export. Type I Secretion. Sec independent - PowerPoint PPT PresentationTRANSCRIPT
Methods of Secretion
Protein Secretion
Type II Secretion (GEP)
• Sec dependent
• Signal peptide
• Chaperone
• 2 Stage
• E.g IgA-protease, Pertussis toxin,
Serratia haemolysin
General Secretion Pathway (Type II)
Type II:Export
Type I Secretion
• Sec independent
• ABC (ATP Binding Cassette)
• COOH recognition peptide
• 1 Stage
• E.g cytolysins, hydrolases,
B. pertussis adenylate cyclase
Type III Secretion
Type III Secretion
• Sec independent
• Secretion co-translational
• Translocation into host cell
• Polar or non-polar secretion
• E.g Yersinia spp. Yops, Shigella IpaB, C & D; EPEC EspA, B, C, Tir
Paradigms of Host-Cell Interactions I: Enterobacter
• Vibrio cholera
• E coli spp.
• Shigella spp.
V. cholerae ingested
Adheres to and colonizes small-intestinal mucosa i(Flagella, Tcp pilother adhesins? Neuraminidase?)
Produces toxins (Cholera toxin,Zot?; Ace?)
Cholera toxin acts on mucosal cells
Extensive fluid and ion loss fromtissues leading to hypotension,electrolyte imbalance and death
Virulence genes expressed(pH shock in stomach,rise in temperature)
Cholera
ToxR
ctxAB toxT
A + B
ToxT
tcpA
Pilin
Other virulencegenes
Enteropathic E coli
• Serotypes and serogroups: e.g O111:H4,O111:H12
• Virotypes: ETECEAggEC
EPECEHEC
EIEC
ETEC
• Similar to V. cholera in symptoms and colonization
• Causes “Traveller’s Diarrhea”
• Two toxins: heat-labile (LT) and heat-stable(ST)
EAGGEC
• Causes persistent diarrhea
• Resembles ETEC in colonization except that adherence to small intestinal cells non-uniform.
• Produce ST-like toxin and hemolysin-like toxin.
EPEC
• Like EAGGEC, adherence also in clumps.
• Causes attachment and effacement lesions.
• More invasive than ETEC or EAGGEC
• Induces inflammatory response.
EHEC
• Can cause acute kidney failure (hemolytic-uremic syndrome [HUS])
• Disease similar to that of Shigella dysentary.
EIEC
• Symptoms similar to Shigella dysentary.
• Actively invades colonic cells with adjacent spread like Shigella, although no toxin produced.
Shigella
Shigella:Ics (Intercellular Spread)
Shigella Virulence Genes