EscT- A Crucial Component of the Type III Secretion System in Enteropathogenic Escherichia coli

One of the most prevalent causes of infantile diarrhea in developing countries is enteropathogenic Escherichia coli (EPEC). EPEC infects intestinal cells by a specialized transport complex, called the type III secretion system (T3SS). T3SSs are used by many Gram-negative bacteria to inject bacterial proteins into eukaryotic host cells in order to promote their own survival and colonization. The base of the T3SS transverses both bacterial membranes and contains an export apparatus that comprises five membrane proteins. Here, we study the export apparatus component, called the EscT protein. EscT is highly hydrophobic, predicated to have 5 transmembrane domains (TMDs) and is expressed to a very low level; therefore, it is technically challenging to characterize this protein. To characterize the EscT protein, we fused a hemagglutinin (HA) tag to the C-terminus of EscT and examine whether the labeled protein retains functional. In this study we discover that EscT is critical for T3SS activity and can be complemented by a labeled protein. Interactions between export apparatus proteins are critical for functionality and stability of the T3SS complex. The investigation of interactions between EscT to another export apparatus components revealed that EscT can directly interact with the core export apparatus protein EscS. We now have a valuable tool to study and detect EscT, hopefully this information will improve our understanding of T3SS complex and provide a possible target to combat infections caused by EPEC and other T3SS-containing pathogens.