Secretion of the Francisella pathogenicity island effector protein PdpE requires components of both the Sec and Type IV pilus secretion pathways.

PdpE secretion in Francisella novicida requires both Sec general secretory components and the Type IV pilus (T4P) pathway, unlike prior T6SS-independent observations.

• Why it matters: The pathway enabling PdpE export was unclear, limiting understanding of how a Type VI secretion island gene product is delivered during intracellular replication and virulence.
• What they did: Using F. novicida, the study tested SecB paralogs and found either SecB supports viability and T4P secretion of chitinase and PepO, but both SecB paralogs are required for T4P-mediated PdpE secretion. Two-hybrid and pulldown assays supported interactions between the two SecB chaperones.
• The result: The dual SecB requirement implies specialized chaperone coordination for PdpE export via T4P, and genomic analyses suggest two secB paralogs are conserved across Francisellaceae, including species lacking pdpE.

AI summary of the abstract · may contain errors · not medical advice · read the paper.