The research in Dr. Swairjo’s lab focuses on elucidating the function and biosynthesis pathways of key modified nucleosides of transfer-RNA using a combination of bioinformatic, biochemical and X-ray crystallographic methods. Our studies of the tRNA modified nucleoside Queuosine led to the discovery and structure determination of the only nitrile reductase enzyme known in biology, and its ongoing development by us and others as a biocatalytic agent for industrial applications, creating an environment friendly alternative to the hazardous chemical methods currently in use. Our studies have also resulted in the identification and full characterization of a new antibacterial drug target that we are currently developing in collaboration with industry using structure-based drug design methods. Because tRNA modifications ensure translational fidelity and control in all life forms, they have been implicated in numerous cell processes in eukaryotes including mitochondrial dysfunction in human neurodegenerative disease. We are presently interested in elucidating the role of these modified nucleosides in mitochondrial function in human neurons and exploring their role in vertebrate development using a zebrafish model.
The crystal structure of the Queuosine biosynthesis nitrile reductase enzyme QueF is an asymmetric tunnel-fold homodecamer of two head-to-head facing pentameric subunits, harboring ten active sites at the interfaces between monomeric subunits, view the video of overall structure and perspective of interfacial catalytic site.
The binding of substrate preQ0 induces closure of the active site, as shown in this video, followed by formation of a thioimide linkage with invariant side chain Cys55. This “induced fit” mechanism of substrate binding may be considered in the re-design of the active site to accept unnatural substrates.