Fig. 1.

Schematic representation of the Shigella type III secretion apparatus (T3SA) and role of IpaB and IpaH proteins. IpaB binds to its cognate chaperone IpgC in the bacterial cytosol. Shigella T3SA extends from the bacterial inner and outer membrane and across the periplasm to form a pore into the host cell plasma membrane. At the tip of this injection needle, IpaB assembles into a pore-forming oligomeric translocon that facilitates delivery of virulence factors. The IpaH family of proteins are effectors secreted through the T3SA and are involved in modulating host immune responses. IpaH suppresses NF-κB activation, which downregulates inflammatory responses