In this video, we're going to introduce phosphorylation cascades. A phosphorylation cascade is when a series of protein kinases amplify a signal by successive phosphorylation events of different kinases. Ultimately, what we are saying is that kinases, which recall from our last video are just enzymes that add a phosphate group to a substrate, are capable of phosphorylating and activating other kinases. This leads to successive phosphorylation events for the amplification of a signal. Let's take a look at our image below of the phosphorylation signaling cascade. Notice once again, we're showing you a cell's plasma membrane right here, and below we're showing you the inside of the cell; above is, of course, the outside of the cell. Notice embedded in the plasma membrane here we have a signaling molecule that is going to be able to bind to the receptor and cause a conformational change.
In a phosphorylation signaling cascade what will happen is a kinase enzyme is going to become phosphorylated and activated in the presence of the signaling molecule binding to the receptor. This activated and phosphorylated kinase can go on to phosphorylate and activate yet another kinase. This kinase here can go on to phosphorylate and activate yet another kinase. Notice that this kinase is different from this one, which is different from this one and so this kinase here might be the one that is responsible for generating the cellular response. But ultimately, what we are seeing here is a phosphorylation cascade, which is really just defined by successive phosphorylation events, one after another, ultimately amplifying the signal to lead for a cellular response.
Phosphorylation cascades are a regular and normal part of many biosignalling pathways. This here concludes our introduction to phosphorylation cascades and, once again, we'll be able to get some practice as we move forward in our course. So, I'll see you all in our next video.