lectins + red blood cells = agglutination

In practical 7 you will be mixing lectins with red blood cells. In this post I want to explain what is actually happening in this mixture...

Red blood cells have sugars on their cell surface. These are either bound to proteins (glycoproteins) or lipids (glycolipids). Either way, the fact is that red blood cells have chains of sugars sticking out all over them.

Lectins on the other hand are proteins that bind sugars. As I said in the previous post, there are many different lectin proteins, that bind different sugars. The important thing for the practical is that lectins bind more than one sugar at one time - i.e. lectins have more than one sugar binding site.

So, what will happen if you mix red blood cells with lectin proteins? Take a look at the following diagram:  

So, to put the above diagram into words: the lectins will bind the sugars on the red blood cells - but that's not all, one lectin might bind sugars sticking out of two different red blood cells and link them together. When a lot of lectin proteins link up a lot of red blood cells you get a weak 3D array of red blood cells held together by lectins - this is called agglutination

You will see what this looks like in the lab....