Regulation of Transcription of the Lac Operon in E.coli. Flashcards
In an environment that lacks lactose, what happens to synthesis of lac mRNA
it is repressed to avoid wasting cellular energy synthesizing necessary enzymes
In an environment that has both glucose and lactose, what happens to synthesis of lac mRNA
cells would rather synthesis glucose since its the central molecule of carb metabolism
In an environment with lactose and not glucose, what happens to synthesis of lac mRNA
cells metabolize lactose at a high rate since glucose is heavily depleted
What is the first of the three genes in the lac operon
B-galactosidase
What are the three protein binding regions in the transcriptional control region
CAP site
lac promoter
lac operator
What is the function of the CAP site
binds catabolite activator protein
What is the function of the lac promoter
binds the sigma 70 - RNA polymerase complex
What is the function of the lac operator
binds the lac repressor
What is the step by step process when lactose is not present in the E.coli. cell
- lac repressor binds to the lac operator
- inhibits transcription initiation via the sigma 70 RNA polymerase
- little lac mRNA is produced as a result
What is the step by step process when lactose and glucose are present in the E.coli. cell
- lac repressor binds to lactose
- dissociates from the operator
- allows sigma 70 RNA polymerase to initiate transcription at a LOW rate
glucose is the preferred synthesis
What is the step by step process when lactose is present but not glucose in the E.coli. cell
- cAMP increases in response to low glucose present
- CAP-cAMP complex binds to the CAP site
- interacts with RNA polymerase to maximize the rate of transcription initiation and transcription of the lac operon
How does the tetrameric lac repressor function
binds to the primary lac operator (O1) and one of the two secondary operators (O2 or O3) simultaneously
