Chapter 18 - Bacterial Gene Expression Flashcards
Why do bacterial use post-translational gene control?
Because most genes are on all the time.
What is lactose composed of?
Glucose and Galactose
How does galactose get into the cell?
Through a channel protein - galactoside permease
What enzyme is needed to cleave lactose?
B-galactosidase
What is the inducer for B-galactosidase?
Lactose
What does the lac l gene code for?
Lac operon repressor - it is upstream of the lac operon
What is an operon?
Genes of similar function that cluster together
What does the lac z gene code for?
B-galactosidase
What does the lac y gene code for?
galactoside permease
Activator
A regulatory protein that binds to DNA and activates transcription. No to little transcription occurs without the activator present.
Where does the repressor bind?
On the operator a little downstream of the promoter.
How does lactose act as an inducer?
Binds to the repressor and causes it to release from the operator
Inducer
Not a regulatory factor- removes repressor
CAP - Catabolite Activator Protein
Activator for lac operon -binds to CAP binding site - strengthens the binding of RNA polymerase to the lac promoter
cAMP
Only when CAP is bond to cAMP can it bind to DNA
When are cAMP levels low?
When glucose levels are high. Thus, CAP isn’t active and transcription doesn’t occur
How is cAMP inhibited?
Glucose inhibits adenylyl cyclase enzyme that phosphorylates cAMP
