Protein secretion

Question 1

Describe 2 step secretion systems

Answer 1

First transport across using sec or tat
The secretion system recognises its substrate in the periplasm
Eg; Type II, Type IV, Type IX, Type X

Question 2

Describe 1 step secretion systems

Answer 2

No sec or tat

Eg; Type I, Type II, Type IV, Type VI

Question 3

Describe Type VI secretion systems

Answer 3

Phage tail contracts on contact with the bacterial surface

This propels the tail tube across the outer membrane and DNA is released from the tail tube into the bacterial cell

Question 4

What is the Type VI secretion system made of?

Answer 4

3 subcomplexes
Transmembrane complex
Baseplate
Contractile tail

Question 5

Describe the transmembrane complex

Answer 5

3 proteins J,L,M

5 fold symmetry

Question 6

Describe the baseplate

Answer 6

Hexameric arrangement

Question 7

Describe the contractile tail

Answer 7

The outer sheath and inner tube
The outer sheath is contractile and made of TssB and Tssc proteins and the distal end is capped by TssA
The inner tube is made up of many Hcp proteins and is rigid

Question 8

How does the contractile tail contract?

Answer 8

TssB/TssC contraction propels the Hcp out of the cell which reveals the binding site for ClpV
ClpV uses ATP hydrolysis to disassemble the sheath