Outer membrane proteins mediate unconventional secretion of <i>Pseudomonas</i> peroxidase through crosstalk between the Sec pathway and outer membrane vesicles

The useful part

They typically assist in maintaining client proteins in a folded state or form pore channels during secretion. However, how OM proteins facilitate the secretion of proteins that lack classical signal peptides remains elusive. Here, we demonstrate that they contribute to the secretion of unconventional B-type dye-decolorizing peroxidase (DypB 2985) in Pseudomonas putida.

How it works

• The lipoprotein, Lpp 1528, which contains a Sec signal peptide, is translocated to the periplasm through the Sec pathway and anchored in the inner leaflet of the OM.
• Following translocation, the two proteins appear to dissociate in the periplasm.
• Lpp 1528 recognizes the C-terminal hydrophobic region of DypB 2985 in the cytoplasm and facilitates its coupling to the Sec machinery for inner membrane translocation, despite DypB 2985 lacking a canonical...
• Subsequently, another OM protein, OmpW 4836, recognizes the N-terminal hydrophobic region of periplasmic DypB 2985 and mediates its incorporation into outer membrane vesicles (OMVs) for extracellular delivery.
• Our study reveals the crosstalk between the Sec pathway and OMVs in the secretion of a non-canonical peroxidase, in which OM proteins, acting as the molecular tethers, mediate the stepwise secretion process.

What to take from it

It expands our understanding of non-classical protein secretion mechanisms and bacterial survival strategies. the identified OMV sorting mechanism offers potential for the further functionalization of OMVs as versatile biotechnological platforms.

Details worth keeping

by Congying Liang, Wenping Zhu, Lu Lin Lipoprotein and OmpW are two major components of the outer membrane (OM) in Gram-negative bacteria and play essential roles in various physiological processes, e.g., protein secretion, folding, and localization.