The structure of NAD+ consuming protein Acinetobacter baumannii TIR domain shows unique kinetics and conformations

Erik Klontz, Juliet O. Obi, Yajing Wang, Gabrielle Glendening, Jahid Carr, Constantine Tsibouris, Sahthi Buddula, Shreeram Nallar, Alexei S. Soares, Dorothy Beckett, Jasmina S. Redzic, Elan Eisenmesser, Cheyenne Palm, Katrina Schmidt, Alexis H. Scudder, Trinity Obiorah, Kow Essuman, Jeffrey Milbrandt, Aaron Diantonio, Krishanu RayMichelle L.D. Snyder, Daniel Deredge, Greg A. Snyder

Research output: Contribution to journalArticlepeer-review


Toll-like and interleukin-1/18 receptor/resistance (TIR) domain–containing proteins function as important signaling and immune regulatory molecules. TIR domain–containing proteins identified in eukaryotic and prokaryotic species also exhibit NAD+ hydrolase activity in select bacteria, plants, and mammalian cells. We report the crystal structure of the Acinetobacter baumannii TIR domain protein (AbTir-TIR) with confirmed NAD+ hydrolysis and map the conformational effects of its interaction with NAD+ using hydrogen-deuterium exchange-mass spectrometry. NAD+ results in mild decreases in deuterium uptake at the dimeric interface. In addition, AbTir-TIR exhibits EX1 kinetics indicative of large cooperative conformational changes, which are slowed down upon substrate binding. Additionally, we have developed label-free imaging using the minimally invasive spectroscopic method 2-photon excitation with fluorescence lifetime imaging, which shows differences in bacteria expressing native and mutant NAD+ hydrolase-inactivated AbTir-TIRE208A protein. Our observations are consistent with substrate-induced conformational changes reported in other TIR model systems with NAD+ hydrolase activity. These studies provide further insight into bacterial TIR protein mechanisms and their varying roles in biology.

Original languageEnglish
Article number105290
JournalJournal of Biological Chemistry
Issue number11
StatePublished - Nov 2023


  • bacterial pathogenesis
  • hydrolase
  • innate immunity
  • nicotinamide adenine dinucleotide (NAD)
  • toll/interleukin-1 receptor (TIR)


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