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 have nucleotide sequences that bind RNA polymerase weakly, which are not close matches to the consensus sequence.
D) they are needed to bind to the allosteric site of RNA polymerase.

Question

Quizplus · Accepted Answer

The promoters of positively controlled operons have nucleotide sequences that bind RNA polymerase weakly, which are not close matches to the consensus sequence. The activator protein is needed to enhance the binding of RNA polymerase to the promoter by interacting with specific sites on the DNA sequence, which helps RNA polymerase recognize and bind to the promoter efficiently. Therefore, without the activator protein, transcription initiation of positively controlled operons would be inefficient.

The Promoters of Positively Controlled Operons Require Activator Proteins,because