Repressors

Question 1

Cro repressor

Answer 1

Lytic growth
Transcribe right
Blocks Lambda
3 helices in HTH
3 beta strands Dimerize
1 helix binds DNA Major groove
dimer binds two major grooves on same side

Question 2

Lambda repressor

Answer 2

Lysogenic growth
Transcribe Left
Blocks cro
5 helices
3 are HTH binding DNA
2 are dimerizing
helices bind to major groove

Question 3

Trp repressor

Answer 3

Core domain: 1,2 dimerize
head domain: 4,5,6 bind dna (5 binds to DNA)
3 connects the domains
conformational change
Binding of ligand activates repressor

Question 4

Lac repressor

Answer 4

Hairpin
tetramer
conformational change
binding of ligand deactivates repressor
5 helices