Catabolite Repression

cAMP = cyclic adenosine mono phosphate

CAP = catabolite activator protein

Complex of CAP-cAMP activates transcription, increases binding of RNA polymerase to lac promotor

If glucose is:	then, cAMP is:	therefore:
present	low	CAP does not bind to CAP site, little transcription if lactose is present; glucose is used up first
absent	high	CAP and cAMP form complex and bind to CAP site to activate high level of transcription if lactose is present

see Fig 18-17 in text