Midterm 2 - Notes 6 (Part 5) Flashcards
What kind of system is VirA?
2 component sensor system
- transduction pathway
What 2 components make up the sensor system?
- VirA (sensor kinase)
2. VirG (response regulator, TF)
What do VirA and VirG do?
They induce transcription of all the Vir genes
What is VirA and VirG required for?
Transcriptional activation of Vir genes
What 3 things are sensed by VirA?
- Phenolics
- pH
- Sugars
What is sugar sensing mediated by?
ChvE
What is ChvE?
It is a chromosomal virulence gene encoding a sugar binding protein
What does sensing results in conformational change lead to?
Activation of kinase domain of VirA
What does VirA phosphorylate?
VirG
- this activates it
What does VirG bind to?
To the promoters of all Vir-operons
How is transcription activated?
By binding VirG to RNA polymerase
OD
Overdrive
What 3 things is T-DNA composed of?
- L border
- R border
- OD sequence
What happens if you delete L?
You get transfer
- but the size will vary
What go you get if you delete R border, but not L?
It abolishes tumourigenesis
What enhances T-DNA transfer?
OD
What are the only 2 elements necessary for T-DNA transfer?
- R border
2. OD
What does VirD1 and VirD2 do?
They encode 2 subunits of a site specific nicking enzyme
What is the site specific nicking enzyme?
Heterodimeric endonuclease
- just cuts one of the 2 strands
What does VirD2 covalently bind to?
5’ end of nicked DNA
What fills in the T-DNA?
DNA polymerase
What does VirC1 do?
It stimulates tumour formation strongly
What does VirC1 bind to?
Binds to OD region next to the R border
What may VirC1 interact with?
VirD1/VirD2 complex
What does VirC1 provide? (2)
- Distinction between R and L
2. Ensures unidirectional excision
What is VirC1?
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
What does VirD4 interact with?
VirD2/T-DNA
What does VirD4 do?
Guides T-DNA to secretion pore
- has additional roles in exporting other proteins
What does VirB form?
An IV secretion pore
- conserved across bacteria
What does the VirB/VirD4 complex do?
It brings VirD2 to the pore and it then brought outside the bacterial cell
Where do VirB proteins span?
Inner and outer membrane
- extends into the extracellular space and attaches to the plant plasma membrane
What process is ATP dependent?
Translocation
What drives the process for VirB/VirD4 complex?
ATP hydrolysis
