Quantification of YopE protein of Yersinia pseudotuberculosis reveals differential secretion rates in other Yops deleted strains

Gram negative pathogenic bacteria Yersinia pseudotuberculosis use a type III secretion system (T3SS) to translocate toxic proteins into the eukaryotic cell. Once these proteins are inside the host cell, they interfere with the cell signalling pathways and alter the cellular response. The genes for the bacterial T3SS are located on the 70-kbp virulence plasmid that is common in all pathogenic species of Yersinia. A tetracysteine tag (FLNCCPGCCMEP) has been introduced in the C terminal end of Yersinia outer membrane protein E (YopE) as a translational fusion to observe secretion of these proteins into host cell that is seen in naturally occurring proteins which allows the expressed fusion protein to be specifically recognised by a biarsenical compound. The Lumio/tetracysteine and FLAsH/tetracysteine labelling system was used to fluorescently label YopE-Tc tag in Y. pseudotuberculosis to observe the secretion and quantification of these specific proteins. In this experiment, different bacterial strains (YPIIIpIB102, YPIIIpIB102(ETC12), YPIIIpIB155(ETC12), YPIIIpIB526, YPIIIpIB529(ETC12), YPIIIpIB604 (ETC12), YPIIIpIB621(ETC12), YPIIIpIB625(ETC12) and YPIII) with different proteins deletion (YopK, YopB, YopE, YopDΔ4-303, YopDΔ4-20 and YopED54-75), with or without tetracysteine tag were used to quantify the expression of YopE. Here, we demonstrated that the proteins YopE exhibit different secretion pattern with the deletion of other proteins. This may allow the possible role of these particular deleted proteins to activate or suppress the secretion of YopE. Overall, data from this experiment suggest that the total YopE expression depends on the conformation of regulator. Key words: Yersinia pseudotuberculosis, T3SS, tetracysteine tag, YopE quantification.