How does Cro cI regulate Lambda lifecycle?
The lambda repressor is a self assembling dimer also known as the cI protein. It binds DNA in the helix-turn-helix binding motif. It regulates the transcription of the cI protein and the Cro protein. The life cycle of lambda phages is controlled by cI and Cro proteins.
How many chains does the Cro repressor monomer contain?
Cro (and repressor) contains a helix-turn-helix (HTH) motif comprising three a helices, as shown at left for a phage l cro monomer bound to a consensus operator half site . Two of these (a2 and a3) are separated by a short turn and are held at 550 with respect to one another.
What is the operator in transcription?
An operator is a genetic sequence which allows proteins responsible for transcription to attach to the DNA sequence. The gene, or genes, which get transcribed when the operator is bound are known as the operon.
Why do promoter mutations cluster at positions and as shown in Figure 11 11?
Why do promoter mutations cluster at positions –10 and –35 as shown in Figure 11-11? Answer: Promoter mutations cluster around the –10 and –35 positions because these are the DNA sequences recognized and bound by the sigma subunit of the polymerase.
How are Ci and Cro repressors related to each other?
Together the Cro and cI repressors form a helix-turn-helix (HTH) superfamily. The lambda Cro repressor binds to DNA as a highly flexible dimer. The crystal structure of the lambda Cro repressor reveals a HTH DNA-binding protein with an alpha/beta fold that differs from other Cro family members, possibly by an evolutionary fold change.
What is the function of the CI repressor protein?
Cited for: FUNCTION. Bacterial cells harboring a lysogenic lambda phage are immune to further infection by lambda. The cI repressor protein inhibits the lytic development of any additional infecting phage particles. The region of the genome that codes for the cI repressor protein is known as the immunity region.
How does the cIII protein protect the cII protein?
The cIII protein acts to protect the cII protein from proteolysis by FtsH (a membrane-bound essential E. coli protease) by acting as a competitive inhibitor. This inhibition can induce a bacteriostatic state, which favours lysogeny. cIII also directly stabilises the cII protein.
How is CI-repressor protein cI-Escherichia phage lambda-CI?
“Multilevel autoregulation of lambda repressor protein CI by DNA looping in vitro.” Cited for: FUNCTION. Bacterial cells harboring a lysogenic lambda phage are immune to further infection by lambda. The cI repressor protein inhibits the lytic development of any additional infecting phage particles.