Specialized shuttle proteins recognize and target type IX secretion effectors

ABSTRACT: Members of the phylum Bacteroidota utilize the type IX secretion system (T9SS) to transport diverse substrates into the environment or onto their surface. T9SS substrates feature a Sec-dependent signal peptide for export to the periplasm and a conserved C-terminal domain (CTD), recognized by the T9SS, for translocation across the outer membrane. Following translocation, substrates engage with a shuttle protein, which ensures their final localization. Almost all CTDs are classified into Type A and Type B families. Well characterized Type A CTDs are all recognized by the PorV shuttle. However, recognition and transport of Type B CTDs remain less explored. Flavobacterium johnsoniae encodes 12 Type B substrates, most often genetically linked to genes encoding PorP/SprF-like shuttle proteins. Here, we demonstrate that two of these Type B substrates indeed rely on their cognate PorP/SprF specialized shuttle proteins for their secretion and identify the shuttle protein responsible for the secretion of three orphan Type B CTDs. Our findings also reveal that five conserved motifs within Type B CTDs are necessary for secretion but not sufficient for their specific recognition by cognate shuttle proteins. Our results further suggest that CTDs contain both a secretion signal, sufficient for recognition and secretion of substrates by the T9SS, and a targeting signal, which directs substrates to their final localization.

INSTRUMENT(S):

ORGANISM(S): Flavobacterium Johnsoniae

SUBMITTER: AUDEBERT Stephane  

LAB HEAD: Dr DOAN Thierry

PROVIDER: PXD065655 | Pride | 2025-09-03

REPOSITORIES: Pride