My Restriction Enzymes, Let Me Show You Them
Why, hello you guys, this is my first post. I’m a medical illustrator, and when I tell people this, it usually elicits question that I must answer with one or more of the following statements. No, I don’t draw all the time (though I can). No, it’s not all textbooks, I mostly make surgical illustrations and animations by way of 3D rendering, though I also occasionally get to create representations at the cellular and molecular level. And no. No, I will not tell you my favorite organ.
This is a 3D illustration of restriction enzymes, just hanging out on some DNA, that I had created for a biotech company. The enzymes are I-AniI, FokI, BspD6I, BbvCI, and Mva1269I. The first three are accessible as crystallography xrays from the open source (yay science!) library, the Protein Data Bank.
Restriction enzymes are like molecular scissors that cut foreign DNA that finds its way into bacteria in what is thought of as a defense mechanism against invading viruses. The host DNA is protected from restriction if it is first methylated. An enzyme will spiral down a length of DNA until a specific sequence is reached, then the ribose backbones of both strands are cleaved in a predictable location. This can create “sticky ends,” which are more staggered, or “blunt ends.”
The laboratory applications for restriction enzymes are basically different ways of manipulating DNA. One is the creation of recombinant DNA, which has endless applications. It allowed for the large scale production human insulin for diabetics using E. coli, as well as for the Hepatitis B and HPV vaccines.
DNA is first digested with restriction enzymes for gel electrophoresis, which is used in gene mapping. That is another subject for another post.
Gene analysis by Southern Blot also utilizes restriction enzymes. This is a way of determining the number of copies of a given gene in an individual, as well as how many mutations are present in a population.
So, in other words, these enzymes are pretty damn important tools in the field of genetics. Their discovery earned Daniel Nathans, Werner Arber, and Hamilton O. Smith the Nobel Prize for Physiology or Medicine in 1978.
This here is an early, but still impressive animation from MacArthur Scholar Drew Berry showing the motion and action of a restriction enzyme. The jitteriness is a representation of brownian motion, which is the apparently random motion of particles at the atomic level. There is something about certain molecular animations that just gets your anthropomorphizing engine going. This can be amusing to us science folk (that kinesin protein really looks like he knows where he’s going!), but bad if you’re the Disco Institute!