Midterm 2 - Notes 6 (Part 5)

Question 1

What kind of system is VirA?

Answer 1

2 component sensor system

- transduction pathway

Question 2

What 2 components make up the sensor system?

Answer 2

1. VirA (sensor kinase)

2. VirG (response regulator, TF)

Question 3

What do VirA and VirG do?

Answer 3

They induce transcription of all the Vir genes

Question 4

What is VirA and VirG required for?

Answer 4

Transcriptional activation of Vir genes

Question 5

What 3 things are sensed by VirA?

Answer 5

1. Phenolics
2. pH
3. Sugars

Question 6

What is sugar sensing mediated by?

Answer 6

ChvE

Question 7

What is ChvE?

Answer 7

It is a chromosomal virulence gene encoding a sugar binding protein

Question 8

What does sensing results in conformational change lead to?

Answer 8

Activation of kinase domain of VirA

Question 9

What does VirA phosphorylate?

Answer 9

VirG

- this activates it

Question 10

What does VirG bind to?

Answer 10

To the promoters of all Vir-operons

Question 11

How is transcription activated?

Answer 11

By binding VirG to RNA polymerase

Question 12

OD

Answer 12

Overdrive

Question 13

What 3 things is T-DNA composed of?

Answer 13

1. L border
2. R border
3. OD sequence

Question 14

What happens if you delete L?

Answer 14

You get transfer

- but the size will vary

Question 15

What go you get if you delete R border, but not L?

Answer 15

It abolishes tumourigenesis

Question 16

What enhances T-DNA transfer?

Answer 16

OD

Question 17

What are the only 2 elements necessary for T-DNA transfer?

Answer 17

1. R border

2. OD

Question 18

What does VirD1 and VirD2 do?

Answer 18

They encode 2 subunits of a site specific nicking enzyme

Question 19

What is the site specific nicking enzyme?

Answer 19

Heterodimeric endonuclease

- just cuts one of the 2 strands

Question 20

What does VirD2 covalently bind to?

Answer 20

5’ end of nicked DNA

Question 21

What fills in the T-DNA?

Answer 21

DNA polymerase

Question 22

What does VirC1 do?

Answer 22

It stimulates tumour formation strongly

Question 23

What does VirC1 bind to?

Answer 23

Binds to OD region next to the R border

Question 24

What may VirC1 interact with?

Answer 24

VirD1/VirD2 complex

Question 25

What does VirC1 provide? (2)

Answer 25

1. Distinction between R and L

2. Ensures unidirectional excision

Question 26

What is VirC1?

Answer 26

It is a protein with OD DNA binding abilities

• role is unclear but it appears to interact and bind to the VirD1 and VirD2 and enhances its efficiency in cutting the DNA
• it can also guide the ss to the pore

Question 27

What does VirD4 interact with?

Answer 27

VirD2/T-DNA

Question 28

What does VirD4 do?

Answer 28

Guides T-DNA to secretion pore

- has additional roles in exporting other proteins

Question 29

What does VirB form?

Answer 29

An IV secretion pore

- conserved across bacteria

Question 30

What does the VirB/VirD4 complex do?

Answer 30

It brings VirD2 to the pore and it then brought outside the bacterial cell

Question 31

Where do VirB proteins span?

Answer 31

Inner and outer membrane

- extends into the extracellular space and attaches to the plant plasma membrane

Question 32

What process is ATP dependent?

Answer 32

Translocation

Question 33

What drives the process for VirB/VirD4 complex?

Answer 33

ATP hydrolysis