Lecture 14 - More Membrane Secretion Flashcards
What is GspE?
An ATPase in type II secretion system
Pilus secretion system similar to T2SS
Type 4 pilus
Type 4 pilus system
1)
2)
3)
Very similar to T2SS
1) PilA (pre-pilin) made with unusual signal peptide –> not recognised by Sec
2) Signal peptidase on CYTOPLASMIC side of membrane cleaves off signal sequence (PilD)
3) PilA secreted through complex very similar to T2SS
Prototypic T3SS
Yersinia YOP
pYV-encoded
Yop
In Yersinia
Contact-dependent T3SS
Normally switched off. Switched on when in contact with another cell.
Inserts proteins into cells that disrupt eukaryotic cell function
Unusual feature of type 4 pilus secretion
Pilus assembly occurs in periplasm
Bacterium that uses type 4 pili
Pseudomonas aeruginosa
Use of type 4 pili
Twitching motility
Type of bacteria that use T3SS
Pathogenic
Effects of Yop insertion on eukaryotic cells
Cytotoxicity
Inhibition of phagocytosis
Apoptosis
Inhibition of cytokine release
Yop pore that breaches host cell membrane
YopB/D pore
Yop B/D function
Membrane pore in host cell
Hydrophobic
Syc
Chaperone of proteins translocated in a T3SS
T3SS protein chaperone
Syc
Is Yop sec-dependent or independent
Independent
Is the N-terminal sequence of Yop proteins cleaved?
No
Generic features of T3SS 1) 2) 3) 4) 5)
1) Needle structure that inserts proteins into target cell
2) Contact-dependent function
3) Sec-independent
4) No periplasmic stage
5) Only in pathogenic bacteria
Which system has many homologous proteins to T3SS?
Flagellum secretion system
T3SS and flagellal basal body look very similar
Type IV secretion system background
Very similar to bacterial conjugation systems
1st protein secreted through a T3SS
Hydrophobic host cell membrane channel
Which type of proteins can be translocated through T3SS needle?
Linear proteins
Number of genes required for a T4SS
At least 10
Best-studied T4SS
VirB11, VirB4 of Agrobacterium tumefaciens
VirB4, VirB11 function
Part of Agrobacterium tumefaciens T4SS
Cytoplasmic ATPases which energise T4SS
Cytoplasmic ATPases in Agrobacterium tumefaciens T4SS
VirB4, VirB11
Uses of T4SS
1)
2)
3)
1) DNA transfer
2) DNA uptake
3) Virulence
4) Pilus formation (in A tumefaciens, for insertion of virulence proteins)
Bacteria which use T4SS
1)
2)
3)
1) Legionella pneumophila
2) Bordatella pertussis
3) Helicobacter pylori
What does pertussis use T4SS for?
Secretion of pertussis toxins
2 different ways that proteins are trafficked through T4SS
1) With periplasmic stage. EG: pertussis toxin
2) Without periplasmic stage. EG: DNA, CagA
How is pertussis toxin secreted
1)
2)
3)
1) Assembled as a preprotein with a typical signal peptide
2) Transferred through Sec
3) In periplasmic space enters T4SS, secreted
T6SS
1) Not very well understood
2) Translocates proteins across bacterial envelope
3) Can insert proteins into target cell using system similar to bacteriophage cell-membrane puncturing protein
Prototypical T6SS
Pseudomonas aeruginosa
Which secretion system shares similarities with bacteriophage membrane-puncturing proteins?
T6SS
T7SS
1) Newly discovered, not well understood
2) Transports proteins across mycobacterial cell wall
3) In G+ bacteria
Name for mycobacterial T7SS
ESX-1 system
In a TB infection, antibodies are produced against which part of T7SS?
CFP10, ESAT6
