This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall goal of this project is to characterize the structures and dynamics of bacterial needle proteins involved in the type III secretion by nuclear magnetic resonance (NMR) spectroscopy. Many bacteria that cause important human diseases require a type III secretion system in order to infect their hosts. A prominent feature of the type III secretion is a tube-like structure, the needle apparatus, which is assembled from the polymerization of a single type of needle protein. The needle apparatus forms a physical contact between the bacterium and the host cell, and has a central channel of 25 that is used to transit bacterial protein toxins into the host cell. We have expressed and purified the monomeric forms of the bacterial needle proteins from Burkholderia pseudomallei and Salmonella typhimurium, BsaL and PrgI, respectively, and have acquired high quality NMR spectra. Our objective is to characterize the NMR structures and dynamics of BsaL and PrgI, and correlate these data to pathogenesis. We have completed the NMR structure of BsaL and showed that it is composed of a two-helix bundle flanked by residues that are in partial helical conformation. We also expect to complete the NMR structure of PrgI this year. We will use NMR backbone dynamics to characterize the motions of these proteins, and assess their roles in the assembly of the needle apparatus, and correlate these data with bacterial pathogenesis. Our work on BsaL represents the first report of an atomic level structure for any type III needle protein, and provides the foundation for further NMR studies aimed at characterizing the structures and dynamics of needle proteins, their protein-protein interactions, and their roles in pathogenesis. We hope to provide the details of how these proteins work at the atomic level, and that knowledge can be used to design novel antibacterial therapy targeted at disrupting the type III secretion system.
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