When living in Chicago, we would often get off on the 31st Street exit on Lakeshore Drive, and at the time there was a sign pointing out some parking areas for McCormick Place. I recall specifically that two of those were labeled "E2" and "E3" and being the gigantic nerd that I am, thought immediately of ubiquitin. Since it is found in every type of cell in all eukaryotic cells, the protein is appropriately named. Check out the cool ribbon model I made of ubiquitin for my students once upon a time, and then let's take a look at ubiquitin's functions in living organisms and how it contributes to health and disease.

A common experimental strategy in studying the effects of a specific protein in cells or organisms is to remove it. One can determine the physiological outcomes in the absence of that protein to ascertain its relative importance in maintaining normal functions, or in some cases, to note that it is dispensable or redundant and might have a backup within the cell to take up the slack. Some targeted techniques include RNA interference (RNAi) and CRISPR-based gene editing, and in many cases, it is possible to generate knockout cell lines or even organisms, like mice, that cannot express a specific protein. But when those strategies are not feasible for the experiment at hand, what is one to do?