The Canadian National Crystallographic Committee will be hosting the sixth Dr. Penelope W. Codding Lecture in support of early career crystallographers on Thursday, January 30, 2025 at 1 PM Eastern (10 AM Pacific). The speaker will be Dr. Nicholas Bragagnolo, York University, Ontario, Canada, who completed his PhD in late 2024.
Biography
Nicholas grew up in a small town in Ontario named Bolton, an hour northwest of Toronto, and currently lives with his wife in Orangeville, two hours northwest of Toronto. His passion for structural biology and crystallography developed during his undergraduate degree (HBSc. in Biochemistry, 2017) at York University through discussions of protein structure with professors Dr. Gerald F. Audette and Dr. Derek Wilson, and with members of the lab of Dr. Katalin Hudak; he completed his undergraduate thesis in the Hudak lab by characterizing the function of a novel isoform of an antiviral protein from a plant called pokeweed. For his graduate studies, Nicholas joined the lab of Dr. Audette at York University, completing a MSc. in Biology (2019) and a PhD in Chemistry (2024) wherein he characterized the structures of proteins related to gram negative bacterial pathogenesis using X-ray crystallography and a variety of biophysical techniques. Currently Nicholas is working as a postdoctoral research fellow at the Hospital for Sick Children under the supervision of Dr. Jean-Philippe Julien. Nicholas is also an award-winning educator having received the Richard Jarrell Excellence in Teaching Award at the graduate level for his work as a teaching assistant and has conducted pedagogical research by working with Dr. Tamara Kelly and the Canadian Consortium for Science Equity Scholars. In his spare time, Nicholas is a professional musician playing jazz drums in the Frank Adriano Quartet.
Abstract: Protein Structure Dynamics in Gram Negative Bacterial Secretion Systems
Bacteria use a variety of secretion systems that enhance their virulence. The conjugative type IV secretion system attributes transmission of mobile DNA elements in bacteria, whereas type IV pili are akin to the type II secretion system and are responsible for host adhesion and twitching motility. Understanding the structure and function of components in these systems would elucidate the mechanisms of bacterial commensalism and antagonism, and would aid in the development of inhibitors to bacterial pathogenesis by disrupting the tools virulent species use for stable, long-term infections.
The entry exclusion protein of the F-like type IV secretion system, TraG, consists of a membrane-bound N-terminal domain and a periplasmic C-terminal domain, denoted TraG*. TraG* is essential in preventing redundant DNA transfer through interaction with a cognate TraS in the inner membrane of the recipient cell to prevent conjugation when the recipient cell carries the same plasmid. Using a multitude of biophysical methods including thermofluor, circular dichroism, collision induced unfolding mass spectrometry, and small angle X-ray scattering, the structural dynamics of TraG* was investigated. This allowed for the characterisation of the 50 N-terminal residues, the 77 C-terminal residues, and the TraS-interacting region of the protein as highly dynamic, providing evidence for the mechanism of the long-distance interactions made by TraG.
This presentation also describes the 1.3 Å crystal structure of the N-terminally truncated type IV pilin of Pseudomonas aeruginosa from strain P1 (ΔP1), the first structure of its phylogenetically linked group (group Ia) to be reported. The structure was solved from X-ray diffraction data collected 20 years ago with a molecular replacement search model generated using AlphaFold. Comparisons of the ΔP1 structure to other type IV pilins using ProSMART indicated that there are cases of higher structural homology between different phylogenetic groups of P. aeruginosa than there are between pilins from the same phylogenetic group, indicating that the classification of pilins based on structural homology may be necessary in developing anti-virulence drugs and vaccines.
To join the lecture: https://ubc.zoom.us/j/61337091196?pwd=JXEa0jxjUs0tCeG7uDoBcM0zM6JskS.1
