The Promoters of Positively Controlled Operons Require Activator Proteins Because

Question

The promoters of positively controlled operons require activator proteins because
A) RNA polymerase easily recognizes the consensus sequence.
B) they are required to inactivate the repressor proteins.
C) the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.
D) they are needed to bind to the allosteric site of RNA polymerase.

Accepted Answer

Positively controlled operons have promoters that bind RNA polymerase weakly and require activator proteins to help RNA polymerase recognize the promoter. The activator protein binds to a specific site on the DNA, called the activator-binding site, and interacts with RNA polymerase to increase its binding affinity to the promoter. This results in an increase in transcriptional activity of the operon.