Christopher J. Thibodeaux, Ph.D

Chemistry Department, McGill University

Assistant professor and Associate Director of the Center for Structural Biology

Correlating Form and Function in Peptide Biosynthetic Enzymes with Structural Mass Spectrometry

Abstract

The reaction catalyzed by class II lanthipeptide synthetase (LanM) enzymes involves dehydration of serine/threonine residues in the LanA precursor peptide, followed by intramolecular addition of cysteine thiols to form thioether bridges. LanM enzymes function in an iterative manner, whereby multiple thioether linkages are installed in a sequential fashion into the maturing LanA intermediate. Collectively, LanM enzymes differ dramatically in their substrate specificities, catalytic efficiencies, and other biochemical properties. The mechanisms underlying this functional heterogeneity remain enigmatic. This talk highlights recent efforts by our lab to untangle the complex relationships between structural dynamics, conformational changes, and biochemical function in LanM enzymes. Using the haloduracin b synthetase (HalM2) as a model LanM system, mass spectrometry-based kinetic studies show that conformational changes and enzyme:peptide interactions influence the kinetics and sequence of biosynthetic events. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) studies show that HalM2 is a dynamic enzyme that undergoes local structural rearrangements and long-range allosteric signalling upon peptide or nucleotide binding. Mutations to previously overlooked, dynamic HalM2 structural elements impact the catalytic activities (dehydration and cyclization) of HalM2, providing evidence that conformational changes and enzyme-peptide interactions contribute to function. Finally, native mass spectrometry coupled to ion mobility shows that HalM2 exists in multiple three-dimensional conformations, and that this conformational landscape is influenced by HalA2 precursor peptide binding and by post-translational modification of the HalA2 core peptide. Cumulatively, our studies illustrate the many benefits provided by mass spectrometry for characterizing the mechanistic and structural properties of peptide biosynthetic enzymes.

Biosketch

Christopher J. Thibodeaux is a native of Louisiana, where he graduated valedictorian with bachelor’s degrees in Biochemistry, Botany, and Chemistry from Louisiana State University. He then entered graduate school in the lab of Hung-wen Liu at the University of Texas, Austin, where his Ph.D. focused on elucidating the chemical and kinetic mechanisms of enzyme catalysis. Following graduation, he had postdoctoral stints in the labs of Taekjip Ha and Wilfred van der Donk at the University of Illinois, Urbana-Champaign, where he studied biomolecular single molecule fluorescence spectroscopy and peptide natural product biosynthesis, respectively. In 2016, he began his independent career in the Chemistry Department at McGill University, where he is currently an assistant professor and serves as Associate Director of the Center for Structural Biology. His research is broadly aimed at combatting the problem of antimicrobial resistance by understanding the detailed molecular mechanisms of enzymes that biosynthesize antimicrobial compounds and enzymes that play roles in bacterial virulence. A sub-focus of his research is to apply mass spectrometry-based techniques to better understand the role of molecular motions in protein function. In his spare time, he enjoys the outdoors, cooking and eating spicy food, large family gatherings, watching (American) football and baseball, and spending time with his wife and three daughters.

Date
Date(s) - September 21, 2023
6:00 pm - 8:30 pm

Emplacement / Location
Université de Montréal - Campus MIL (Beer and pizza at 18h, conference at 19h in A-4502)