In this video, we're going to introduce repressible operons. A repressible operon is usually one that is normally turned on, and therefore its genes are expressed. It is termed a repressible operon because, even though it is typically on, it can be turned off or repressed under the right conditions, which includes having an active repressor protein. It's important to note that the inactive repressor protein cannot repress transcription without a co-repressor molecule. The co-repressor is a small molecule itself that will bind to the repressor, forming an active repressor protein. In other words, the co-repressor molecule activates the repressor protein so that transcription is turned off when there is an active repressor protein.
Let's look at the image below to get a better understanding of a repressible operon. A repressible operon aligns with negative gene regulation because the gene can be turned off under specific conditions. Normally, repressible operons are turned on. When they are turned on, RNA polymerase binds and transcribes, forming mRNA, which then gets translated into gene products. The genes are expressed because the repressor is in an inactive form. We have an inactive repressor protein that cannot bind to the operator since it requires a co-repressor to bind. Under specific conditions, if there is a co-repressor molecule, represented by a little red molecule, this co-repressor can bind to the inactive repressor to form an active repressor. The active repressor can bind to the operator, preventing transcription, thus turning off the gene and the operons. Repressible operons are normally on but can be turned off under the right conditions, which includes having a co-repressor molecule present. Notice the image of the switch being turned off, symbolizing the functionality of repressible operons being turned off.
This concludes our brief introduction to repressible operons, and we will be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.
