Researching a Selective Antibacterial Effect Against Streptococcus mutans

Kirk Hevener, PharmD, PhD, assistant professor of Biomedical and Pharmaceutical Sciences at Idaho State University, College of Pharmacy, explains his research regarding topoisomerase I and II enzymes.

Interview Transcript (slightly modified for readability)

“We started the project about a year and a half ago, by doing the molecular cloning and starting to purify the protein. Initial steps in my laboratory have been characterizing the protein in terms of how can we purify it, what protocols do we need to purify it, and what assays should we develop to actually test compounds.

The work that I’m presenting today involves the development of our expression and purification protocol and also our preliminary work in the development of assays that can be used to test compounds. Moving forward from this, we’re going to be doing two things: the first is x-ray crystallographic characterization of the 3-D structure of this protein. So, we’re going to try to solve the 3-D structure in my lab using x-ray crystallography, a type of structural biology.

Once we have that three-dimensional structure, we can use computers to design compounds that can bind into the active site and hopefully inhibit the protein. The second thing that we’re going to do is we’re going to scale up the assays that we’ve already developed for screening large compound libraries, experimental libraries, in the hopes of identifying compounds that can inhibit the activity of this protein.

Once we identify compounds that inhibit the enzyme, the topoisomerase I enzyme, then we’ll take those into what I call ‘wholesale antibacterial testing’. We’ll see [if] compounds that inhibit topoisomerase I kill or inhibit the growth of the bacteria, specifically in our case, Streptococcus mutans. If it inhibits the growth or kills the bacteria [and] has what we call a bactericidal activity, then we’ll test those compounds against other organisms that are the beneficial bacteria that have both topoisomerase I and topoisomerase III to see if there is less of an effect as per our hypothesis with bacteria that have both of the type I topoisomerases compared to the Strep mutans that only has the one. Ideally, we’ll see a selective antibacterial effect against Streptococcus mutans, confirming our hypothesis.”