β-Lactam containing antibiotics are some of the world’s most widely used drugs. The clinical and agricultural overuse of these antibiotics holds a heavy responsibility for the antibiotic resistance that we see in the clinic. One mechanism by which bacteria acquire resistance is through the expression of β-lactamases, which degrade β-lactam containing antibiotics. The metallo-β-lactamases (MBLs) are one class of β-lactamases, which contain one or two zinc ions within their active site that are essential for catalytic activity. One approach to extend the lifespan of our current β-lactam antibiotics is to identify inhibitors of the MBLs. A compound that inhibits the MBLs would allow β-lactams to cause cell death, and a combination therapy of the inhibitor plus the β-lactam could prove to be an effective means to treat antibiotic resistant bacterial infections. Indeed, such combination therapies (<i>i.e.</i>, Augmentin<sup>R</sup>) have been used for decades to treat serine β-lactamase producing bacterial infections. My project involves ascertaining the mode of inhibition of these inhibitors and providing information that will be used to redesign the compounds to exhibit better inhibition and microbiological activities. Using several spectroscopic techniques (CD, NMR, EPR, and UV-Vis), all of which require MBLs with paramagnetic (unpaired electrons) metal ions, the active sites of MBLs can be probed. Importantly, the Co(II)-substituted analogs of MBLs are catalytically active (with roughly 75% of the catalytic activity of the Zn(II)-containing enzyme), and structural studies have shown nearly identical structures for the two analogs. Herein, a new EPR study is being developed, focusing on two types of EPR, continuous wave (CW) and double electron-electron resonance (DEER). These two techniques will allow us to probe the position of the active site loop found in all clinical MBLs upon inhibitor binding. Understanding the positions of the loop upon inhibitor binding will allow us to determine if the inhibitors interact with the loop. Those inhibitors that form more active site contacts are hypothesized to exhibit increased residence times of the inhibitor in the active site, increasing the specificity of that MBL inhibitor.

Spectroscopic studies on metallo-β-lactamases and inhibitors

2019 Spring National Meeting

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