CAREER: CAS: Spectroscopic Investigations of Biological Tellurium and Selenium Detoxification

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Tellurium (Te) is a toxic chemical element that poses a potential problem as an environmental contaminant as a result of its increased use in electronics, mining, batteries, and optics. A set of related tellurium ion resistence (TeR) proteins have been discovered in bacteria that are able to survive exposure to tellurium ions. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Kelly N. Chacón from Reed College to use cutting edge light-based measurements to characterize the structural and biochemical properties of these bacterial TeR proteins. Understanding these proteins helps explain the relatively unknown biological reactions of tellurium, while exploring potential bioremediation methods for mining Te as a precious resource and detoxifying Te from contaminated soil. With this award, Dr. Chacón uses an assertive, multifaceted approach to increase the retention of students from underrepresented minority groups in the science, technology, engineering, and mathematical (STEM) disciplines. Her program increases inclusiveness in the STEM curriculum by emphasizing practices based on the principles of belongingness, capacity, and interest. She is hosting a yearly two-day conference and workshop that will bring graduate students of color and “other” (including diverse gender, low-social economic status and first generation groups) from across the country to Reed College to provide a broader view of science and scientists to students at this small liberal arts college. The discovery of tellurium-resistant (TeR) bacteria has led to the identification of a plasmid-encoded tellurium-resistance operon. There is a large gap in our knowledge of structure and function of the proteins expressed from the TeR genes. Furthermore, a paucity of information exists on the biochemical role of Te, despite its similarity to the other essential chalcogens (oxygen, sulfur, and selenium). The soluble anions tellurite (TeO3[2-]) and tellurate (TeO4[2-]) are xenobiotic compounds. Little is understood about the biochemistry of their toxicity and efflux. Bacteria must contend with exposure to non-essential toxic metals and expend energy toward rapid detoxification, and many have developed resistance to Te. Dr. Kelly N. Chacón will apply a combination of fundamental biochemistry, Selenium/Tellurium/Arsenic k-edge Extended X-ray Absorption Fine Structure (EXAFS), Cryo-electron microscopy (Cryo EM), and crystallography to characterize the essential TeR protein components and begin to fill in the blanks of fundamental Te biochemistry. In addition to giving new insight into chalcogen bioinorganic chemistry, understanding of the TeR proteins could potentially provide an intriguing Te bioremediation method for mining this precious resource and for detoxifying contaminated soil.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.