Secretion systems

Question 1

Type I substrate

Answer 1

proteins, including RTX toxins, cell surface layer proteins, proteases, lipases, bacteriocins, heme acquisition proteins and etc. , drugs

Question 2

Type II substrate

Answer 2

signal peptide containing precursor proteins. Folded proteins.

Question 3

Type IV substrate

Answer 3

 DNA – for conjugation

 proteins, protein complexes, nucleoprotein complexes.

Question 4

Type I pumping mechanism

Answer 4

can be primary (ABC) or secondary (SMR, MATE, etc)

Question 5

Type II pumping mechanism

Answer 5

Sec translocon binds precursor. Leader peptidase (e.g. peptidase GspOa?) cleaves signal peptide and the protein is released into the periplasm. Powered by an NTPase. This is the general export pathway.
 Tat can be used rather than Sec; Pseudomonas exports phospholipases this way. Signal peptides have a twin arginine motif.

Question 6

Type V pumping mechanism

Answer 6

No energy coupling or accessory proteins.

Question 7

Type I across the inner membrane

Answer 7

pump protein

Question 8

Type IV across the inner membrane

Answer 8

 Core complex spans both inner and outer membrane. Made fro VirB7, VirB9 and VirB10. Self assembling

Question 9

Type V across the inner membrane.

Answer 9

 N terminal leader initiates inner membrane transport.

Question 10

Across the periplasm: Type I

Answer 10

TolC, adaptors.

Question 11

Across the periplasm: Type IV

Answer 11

 Core complex spans both inner and outer membrane. Made fro VirB7, VirB9 and VirB10. Self assembling

Question 12

Across the outer membrane: type I

Answer 12

TolC

Question 13

Across the outer membrane: type II

Answer 13

2 proteins located in OM.

Question 14

Across the outer membrane: type IV

Answer 14

 Core complex spans both inner and outer membrane. Made fro VirB7, VirB9 and VirB10. Self assembling.

Question 15

Across the outer membrane: type V

Answer 15

 C terminal helper domain necessary.

 IgA1 protease cleaves away from membrane bound sequence

Question 16

Purpose of type I

Answer 16

export of toxins, other proteins and drugs.

Question 17

Purpose of type II

Answer 17

main terminal branch of General secretory pathway.

Question 18

Purpose of type II

Answer 18

delivery of proteins by 
	Yersinia
	 Salmonella
	Shigella
	Bordetella
	Pseudomonas.
Also used in type IV pilus formation.

Question 19

Purpose of type IV

Answer 19

 Conjugation
 Virulence protein injection (H. Pylori, Brucella suis, Legionella pneumophila) and secretion (Bordetella pertussis)
 Mediating DNA release and uptake (H. Pylori, Neisseria gonorrhoeae)

Question 20

Purpose of type V

Answer 20

 Autotransporters
 2 partner system
 Vc or AT-2

Question 21

Type IV pilus structure

Answer 21

Tip adhesin
Major pilus subunit
Base of structure
Other

Question 22

Type IV tip adhesin

Answer 22

• P. Aeruginosa tip adhesin PilY1 binds asialoGM1/2

* Neisseria tip adhesin binds CD46

Question 23

Type IV major pilus subunit

Answer 23

PilA

Question 24

Type IV base of structure

Answer 24

• PilQ = channel in OM
• PilC essential inner membrane protein
• PilB energises assembly via hydrolysis of NTPs.
• PilT energises retraction and recycling of pilins.

Question 25

Type IV pilus structure - other

Answer 25

• PilD is a specific peptidase on the inner membrane, cleaves signal peptide for Sec pathway on secreted proteins.