Chaperone DegP Is Not Necessary for the Polyhistidine Tag-Detected Secretion of Autotransporter BrkA in Escherichia coli BW25113

Résumé

Autotransporters are virulence-associated proteins capable of independent secretion, present on the outer membranes of Gram-negative bacteria. Bordetella pertussis is the causative agent of whooping cough and expresses the 103 kDa type Va autotransporter Bordetella resistance to killing (BrkA), which contributes to the bacterium’s resistance against the bactericidal activity of the complement pathway. The exact folding mechanisms, including the role of periplasmic chaperones involved in the translocation of BrkA, are not well understood. DegP is a highly conserved periplasmic chaperone that has been implicated in the folding and secretion of other autotransporters in Escherichia coli but has yet to be characterized in the expression of BrkA. We therefore hypothesized that DegP would be necessary for BrkA secretion. To investigate this, a 6x histidine tag was inserted in the unstructured region of the BrkA passenger domain for detection by immunoblot analysis. We compared the expression between WT BW25113 and mutant JW0157 (ΔdegP) cells and observed BrkA surface expression in both conditions, indicating that DegP is not necessary for BrkA secretion. This study provides insight into the secretion process of the virulence factor BrkA and bacterial membrane transport systems which holds the potential for the development of new clinical interventions and biotechnological applications.