In this video, we're going to begin our lesson on eukaryotic post-translational regulation. Eukaryotes can regulate expression at the post-translational level by controlling the activity of the expressed protein. Recall from our previous lesson videos that post-translational modifications can be abbreviated as PTMs. They are defined as covalent modifications to proteins after translation takes place, which is what the "post" root here is referring to; "post" means after. These post-translational modifications or PTMs can either activate or inactivate a protein, depending on the specific protein and the specific scenario. They can also tag the protein or mark the protein for degradation by proteases. Proteases are specific enzymes that degrade proteins by breaking polypeptide bonds, the bonds that link amino acids together. By breaking and degrading proteins, proteases are capable of making single amino acids.
If we take a look at our image down below, we can get a better understanding of these post-translational modifications. Protein activity can be controlled by post-translational modifications or degradation by proteases. Looking at our little mini-map, you'll notice that post-translational protein modifications occur in the cytoplasm of the cell. Up above, what we're showing you is the mRNA here that's going to be translated into a protein. But in many cases, proteins that are initially translated can be inactive proteins. The post-translational modification here includes a modification tag, basically covalently modifying the protein to create an active protein. This is a form of turning on a gene after translation has occurred. Again, this is through post-translational modification, a modification that occurs after translation has occurred. Post-translational modifications can also inactivate a protein, so it is also a form of turning off a gene.
Now down below what we're showing you is again an mRNA being translated into a protein, and this time, there is a modification tag being added to the protein. But this time, this tag is actually marking the protein for degradation by this protease enzyme. The protease enzyme in blue is going to perform protein degradation to break up that protein into individual amino acids. Of course, if we are degrading the protein, then that is a form of turning off the gene, a form of regulation. Through post-translational modifications, proteins can be turned on or off, depending on the specific scenario. This here concludes our brief introduction to eukaryotic post-translational regulation, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
