This week we feature four new videos for our editor's picks collections selected by Dr. Justin Cherny, one of our Science Editors.
Dr. Cherny: Here’s the basic concept. You take all the proteins in an organism, and you put them into a bag. You have billions of proteins, but let’s say you really only care about two of them. How would you find those? That’s what these articles are about.
Pick #1 — "Identifying Protein-protein Interaction in Drosophila Adult Heads by Tandem Affinity Purification (TAP)"
Dr. Cherny: In this video, think of the bag as a Drosophila head. There are all different kinds of cell types in there. If you want to study a protein made up of four different protein partners—proteins A, B, C and D—you take one of those partners, let’s say B, and you manipulate it in the organism so it has a tag labeling it. In the TAP method described in this video, the researchers first express a tagged version of protein B in vivo, and then they pull it out of the bag. When you do this, protein B also pulls proteins A, C, and D with it. This is because of affinity, or, these proteins’ natural tendency to aggregate. It’s with this method that scientists can determine which proteins interact with each other.
Pick #2 — "Membrane-SPINE: A Biochemical Tool to Identify Protein-protein Interactions of Membrane Proteins In Vivo"
Dr. Cherny: Here we have the same concept as in the TAP video, but this time we’re focusing on cell membrane proteins. What you do is you send B in as bait, looking to pull out A, C and D. It’s basically like you’re fishing. Membrane proteins are embedded in cellular membranes and have hugely important functions. The researchers in this video are looking to study those functions—cellular communication, endocytosis, exocytosis—for many reasons. For example, their malfunction can be the cause of certain types of cancer.
Pick #3 — "Budding Yeast Protein Extraction and Purification for the Study of Function, Interactions, and Post-translational Modifications"
Dr. Cherny: Before we were just looking at who was binding to whom, but now we’re pulling particular proteins from the bag and looking at how they’re modified. Are they phosphorylated? That kind of thing. The process of making a protein is called translation. The study of post-translational modifications (PTMs) refers to looking at proteins after they’ve been modified. This is done by the cell itself. In fact, it’s done by other proteins. The cell makes modifications to a given protein’s chemical structure, adding certain things like phosphorylation sites. PTMs change the shape of proteins, which is important in protein function. This strategy allows you to purify these proteins, and examine them for cases of Phosphorylation.
Pick #4 — "Total Protein Extraction and 2-D Gel Electrophoresis Methods for Burkholderia Species"
Dr. Cherny: Let’s say I’m not interested in any one protein in particular, but I want to see all of the proteins all at once. I take my bag of proteins, and I run them two ways. SDS PAGE separates them by their mass. But imagine you have 1000 proteins that all weigh the same. You have to add another dimension of separation—electrophoresis. Instead of just pulling it top to bottom, now you’re going to also pull them side to side using how positively and negatively charged each protein is. Then, if you are interested in a protein that you’ve separated, you could submit this data for analysis by mass spectrometry.
Having trouble viewing these videos even though your institution subscribes to JoVE? Click here to recommend to your librarian.
