∞ generated and posted on 2016.02.14 ∞

Sequence of nucleotides to which a transcriptional regulatory protein or proteins can bind.

The idea of operator is associated with but not identical to that of operon.

From , pp. 8 and 9:

We will often say that a particular regulatory protein binds to a specific operator site (or sites) on a DNA molecule. We mean by this that the protein is usually to be found there, but that it can quite readily (and often does) fall off that site. Whether another identical protein quickly binds again depends upon its concentration and its affinity for the DNA site.&parr;A DNA molecule may have more than one site able to bind a particular protein. Such sites can vary in the strength with which they bind the protein. If one site is weaker than another then, at any given instant, and at low protein concentrations, the stronger site is more apt to have a protein bound to it. …at high protein concentrations the difference in affinities would be ignored and both sites would usually be filled. This state of dynamic equilibrium obtains because the bonds involved in protein-DNA interactions are much weaker than those (for example) that hold the links of the protein chain together. … Binding of a regulatory protein to a strong and a weak operator site. A regulatory protein fills only the strong operator site at low concentration, but fills both operator sites at high concentration. Put another way, the protein first binds the strong site, then the weak site, as its concentration increases.