Graduate Student Madhura Damle

"Characterization of Zinc Binding Proteins in Bacteria"

In the recent years, the world has seen a steep rise in antibiotic resistance that hinders our ability to fight deadly diseases such as tuberculosis and pneumonia1. Over prescription of antibiotics is one of the many reasons for the growing problem. At least 2.8 million people in the United States alone are infected by bacteria that are antibiotic resistant2. In recent times, researchers have defined a new term known as ‘nutritional immunity’ where the host sequesters essential metals from the pathogenic bacteria in an effort to ‘starve’ them. Conversely, the host can direct the excess supply of metals towards the bacteria as a means to combat the infection3. The bacteria have sophisticated machinery in place to tightly control the level of metals in the cell.

The focus of this work is the zinc binding proteins in bacteria that have been linked to zinc homeostasis. Specifically, the work focuses on the azt and znu ABC transporter operons that are controlled by the transcriptional regulator zur4–6. zur has been shown to act as a repressor as well as an activator depending on the varying zinc concentrations in the cell4. AztD in P. denitrificans has been shown to act as a metallochaperone to AztC and its structure has been solved using X-ray crystallography in an effort to understand its interaction with AztC6. Additionally, the protein ZnuA has been studied in vitro to determine the number of Zn binding sites, affinity and its relationship with AztD5.
This research will provide insights into how the proteins function and interact with one another to maintain zinc levels to avoid toxicity or starvation. This knowledge will, in turn, provide a good foundation to the study of development of antibiotics that will eventually tackle the problem of antibiotic resistance.

Bibliography:

(1) Antibiotic resistance https://www.who.int/news-room/fact-sheets/detail/antibiotic-resistance (accessed Apr 24, 2021).
(2) CDC. What Exactly is Antibiotic Resistance? https://www.cdc.gov/drugresistance/about.html (accessed Apr 24, 2021).
(3) Hood, M. I.; Skaar, E. P. Nutritional Immunity: Transition Metals at the Pathogen-Host Interface. Nat. Rev. Microbiol. 2012, 10 (8). https://doi.org/10.1038/nrmicro2836.
(4) Choi, S.-H.; Lee, K.-L.; Shin, J.-H.; Cho, Y.-B.; Cha, S.-S.; Roe, J.-H. Zinc-Dependent Regulation of Zinc Import and Export Genes by Zur. Nat. Commun. 2017, 8 (1), 15812. https://doi.org/10.1038/ncomms15812.
(5) Neupane, D. P.; Kumar, S.; Yukl, E. T. Two ABC Transporters and a Periplasmic Metallochaperone Participate in Zinc Acquisition in Paracoccus Denitrificans. Biochemistry 2019, 58 (2), 126–136. https://doi.org/10.1021/acs.biochem.8b00854.
(6) Neupane, D. P.; Fullam, S. H.; Chacón, K. N.; Yukl, E. T. Crystal Structures of AztD Provide Mechanistic Insights into Direct Zinc Transfer between Proteins. Commun. Biol. 2019, 2 (1), 308. https://doi.org/10.1038/s42003-019-0542-z.