Obtaining Structural Insights on Bacterial Protein Complexes Using Time-Resolved Hydrogen-Deuterium Exchange Mass Spectrometry
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Persistent infections by Pseudomonas aeruginosa are initiated by interaction of a type IV pilus (T4P) with receptors on the mucosal cells of susceptible hosts. Here, we examine the structural changes occurring between the monomeric and dimeric states of ΔK122 using time-resolved electrospray ionization hydrogen-deuterium exchange mass spectrometry (TRESI-HDX-MS). Based on levels of deuterium uptake, the N-terminal α-helix and the loop connecting the second and third strands of the anti-parallel β-sheet contribute significantly to pilin dimerization. Conversely, the antiparallel β-sheet and αβ loop region exhibit increased flexibility, while the receptor binding domain retains a rigid conformation in the equilibrium state. Additionally, Escherichia coli are able to adapt to changing environmental conditions and develop antibiotic resistance through a process called F-plasmid conjugation, carried out through a type IV secretion system (T4SS). The F-T4SS protein TraF is of particular interest due to its involvement in pilus assembly to mediate the transfer of DNA. Dynamic analysis of a GST-TraF construct through TRESI-HDX-MS was performed to gain further insights on its structure. These studies have revealed that the C-terminal region predicted to contain the thioredoxin-like domain is quite structured compared to the more solvent accessible N-terminal region predicted to form a protein-protein interaction with companion T4SS protein TraH. Structural analysis of a GST-TraF construct is on-going to further characterize the regions responsible for protein-protein interaction and the elucidation of its three-dimensional structure.