BIO206H5 Lecture Notes - Lecture 18: Catabolite Activator Protein, Lac Operon, Community Access Program
Document Summary
Positive regulation is mediated via the effect of the catabolite activator protein of the. This interaction stabilizes the protein on the promoter region. So it increases the binding af nity of the rnapol for the promoter. In the presence of the dimer, it encourages and promotes the stable binding of rna pol which then leads to frequent transcription of the lac operon. So as a positve regulator, it is the cap plus camp molecule. Thats the positive regulator of this component. In the absence of the camp, we have the cap protein, but it binds relatively poorly ot he cap site of the promote. So there"s infrequent cap binding, that leads to less frequent less stable rna pol at the promoter. So as a consequecne, it will bind and transcribe that gene. But the rate of transcription is pretty low because we cant get a stable bond at the promoter. Eg: with camp we may have 100 successful binding/second.