Satellite Program Oral The 48th Lorne Conference on Protein Structure and Function 2023

Structural and Functional Characterization of Bacterial TIR Proteins (#37)

Sulin Li 1 , Mohammad Kawsar Manik 1 , Thomas Ve 2 , Jeffrey D Nanson 1 , Bostjan Kobe 1
  1. School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, Australia
  2. Institute for Glycomics, Griffith University, Southport, QLD, Australia

 Bacterial Toll/interleukin-1 receptor (TIR) domain-containing proteins have been shown to mediate to the pathogenicity and anti-viral activity of bacteria. During bacterial infection, TIR domain-containing proteins may act as virulence factors to inhibit immune responses by interfering with Toll-like receptor signalling. Additionally, some bacterial TIR domain-containing proteins possess NAD+ nucleosidase activity, which is not only also related to the virulence of pathogenic bacteria, but also plays an important role in bacterial anti-viral defence 1, 2. Here we report our studies on two bacterial TIR domain-containing proteins: PumA and AbTIR. Acinetobacter baumannii TIR domain-containing (AbTir) is one of the few bacterial proteins that has been reported to produce v-cADPR after NAD+ nucleosidase. We determined the crystal structure of AbTir TIR domain and the structure of v2-cADPR. Furthermore, we found that addition of an inhibitor of AbTir NAD+ nucleosidase activity (3AD) induces the formation of AbTir TIR domain filaments, and appears to trap the protein in an active conformation. Using cryoEM, we successfully determined the AbTir filament structure. Recent studies showed that PumA, which is from multi-drug resistant pathogen Pseudomonas aeruginosa PA7, is essential for PA7 strain virulence 3. We determined that PumA also has NAD+ nucleosidase activity. We also saw observed AbTir TIR domain filaments upon incubation with 3AD. Further structural and functional studies will determine the structure of these filaments and investigate the role these assemblies play in bacterial virulence and anti-viral defence.

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