Job Candidate Seminar: Dr. Natalie Krahn, "Expanding the Chemical Diversity of Proteins"

"Canonical protein synthesis occurs through the translation of mRNA; where 61 sense codons decode 20 amino acids. With only 20 amino acids, the chemical variability and therefore protein functionality is limited. To expand the chemical diversity, nature has developed pathways to install post-translational modifications as well as translation systems to repurpose termination codons. For the latter, recoding termination codons expands the natural amino acid library by two: pyrrolysine and selenocysteine. Selenocysteine (Sec), the 21^st amino acid, is structurally similar to cysteine (Cys) but with a selenium moiety instead of sulfur. As a result, Sec participates in many of the same chemical reactions as Cys, but often with enhanced catalytic and redox properties. Replacing Cys active sites with Sec can increase catalytic efficiency >100-fold, while strong diselenide bonds (Se-Se) are readily formed. The potential for functional gain or added stability with introducing Sec into proteins (selenoproteins) expands their capabilities. However, the complexity and added factors for selenoprotein synthesis have limited their study. To overcome this barrier, we have developed tools and technologies to facilitate the insertion of Sec into any desired protein in Escherichia coli. This breakthrough has enabled the production of synthetic selenoproteins to uncover the remarkable capabilities of Sec."

- Dr. Krahn's abstract