Structural Analysis of SPI-2 needles

Salmonella Pathogenicity Island-2 (SPI-2) plays a central role in the intracellular survival of Salmonella by encoding a type III secretion system, whose structure is currently unknown. SPI-2 gene expression is controlled by the two-component regulatory system SsrA/B, whose expression is in turn controlled by additional regulatory networks. The type III secretion system that is encoded by SPI-2 has not been well-studied, in part because it is not abundant and also because other surface appendages such as pili and flagellae obscure its visualization. Yet without SPI-2 type III secretion, Salmonella is unable to launch a systemic infection and becomes avirulent.

We are using cryoelectron microscopy (cryoEM) in collaboration with Dr. Wah Chiu (Baylor College of Medicine) to perform a structural analysis of the macromolecular complex of the SPI-2 secretory apparatus in order to fully study structural and assembly aspects of SPI-2 secretion.

Phase contrast and fluorescence images of SsaC-GFP fusion strain, S. Typhimurium (14028s). The outer ring protein SsaC-GFP fusion was expressed from an arabinose-induced plasmid (pMPM-K6Ω) in a ΔssaC background. The strain was grown in PCN (pH 5.8) at 37˚C for 4h. 2 μm scale bars.

Researchers: Hideaki Mizusaki
Lab: Linda J Kenney Lab