Question

What kind of molecule is the lac repressor?

Answer 1

A repressor is a DNA or RNA-binding protein that regulates the expression of one or more genes by binding to the operator or related silencers, according to molecular genetics. A DNA-binding repressor prevents RNA polymerase from attaching to the promoter, blocking the transcription of genes into messenger RNA.

Complete answer:
Lac repressor is a DNA binding protein that is encoded by the lac operon's gene 'i'. It binds to the operator region, which is located next to the promoter area, and suppresses RNA polymerase transcription.

Lac repressor is a DNA-binding protein that suppresses the expression of genes that code for proteins involved in the lactose metabolism in bacteria. When lactose is not available to the cell, these genes are repressed, ensuring that the bacterium only invests energy in the development of machinery required for lactose uptake and utilisation when lactose is present. Lactose is transformed to allolactose when it becomes accessible, inhibiting the lac repressor's capacity to bind to DNA and so enhancing gene expression.

The lac repressor is a protein that suppresses (represses) lac operon transcription. It accomplishes this by binding to an operator that partially overlaps the promoter. The lac repressor binds to the RNA polymerase and prevents it from transcribing the operon.

An example of an inducible system is the lac operon. The binding of the effector molecule to the repressor greatly increases the repressor's affinity for the operator, and the repressor binds and stops transcription in repressible systems.

Note: In E.coli and many other enteric bacteria, the lactose operon (lac operon) is necessary for lactose transport and metabolism. Although glucose is most bacteria's preferred carbon source, the lac operon enables for successful lactose digestion when glucose isn't available due to the activity of beta-galactosidase.