The assembly of the bacterial flagellum is orchestrated by the secretion of distinct early and late secretion substrates via the flagellar-specific type-III secretion system (fT3SS). However, how the fT3SS is able to distinguish between the different (early and late) substrate classes during flagellar assembly remains poorly understood. In this study, we investigated the substrate selectivity and specificity of the fT3SS of Salmonella enterica at different assembly stages. For this, we developed an experimental setup that allowed us to synchronize hook-basal-body assembly and to monitor early and late substrate secretion of fT3SSs operating in either early or late secretion mode, respectively. Our results demonstrate that the fT3SS features a remarkable specificity for only the substrates required at the respective assembly stage. No crosstalk of substrates was observed for fT3SSs operating in the opposing secretion mode. We further found that a substantial fraction of fT3SS surprisingly remained in early secretion mode. Our results thus suggest that the secretion substrate specificity switch of the fT3SS is unidirectional and irreversible. The developed secretion substrate reporter system further provides a platform for future...Continue Reading
Rapid turnover of FlhD and FlhC, the flagellar regulon transcriptional activator proteins, during Proteus swarming.
Domain structure of Salmonella FlhB, a flagellar export component responsible for substrate specificity switching.
Completion of the hook-basal body complex of the Salmonella typhimurium flagellum is coupled to FlgM secretion and fliC transcription
Substrate specificity of type III flagellar protein export in Salmonella is controlled by subdomain interactions in FlhB
Sorting of early and late flagellar subunits after docking at the membrane ATPase of the type III export pathway.
Interaction of FliK with the bacterial flagellar hook is required for efficient export specificity switching.
Interactions of bacterial flagellar chaperone-substrate complexes with FlhA contribute to co-ordinating assembly of the flagellar filament
Comparative analysis of the secretion capability of early and late flagellar type III secretion substrates
Role of autocleavage in the function of a type III secretion specificity switch protein in Salmonella enterica serovar Typhimurium
Scarless deletion of up to seven methyl-accepting chemotaxis genes with an optimized method highlights key function of CheM in Salmonella Typhimurium
The role of intrinsically disordered C-terminal region of FliK in substrate specificity switching of the bacterial flagellar type III export apparatus
Insight into structural remodeling of the FlhA ring responsible for bacterial flagellar type III protein export
Bacterial type III secretion systems: a complex device for the delivery of bacterial effector proteins into eukaryotic host cells
The Structure of an Injectisome Export Gate Demonstrates Conservation of Architecture in the Core Export Gate between Flagellar and Virulence Type III Secretion Systems.
FliK-driven conformational rearrangements of FlhA and FlhB are required for export switching of the flagellar protein export apparatus
The flexible linker of the secreted FliK ruler is required for export switching of the flagellar protein export apparatus.
The substrate specificity switch FlhB assembles onto the export gate to regulate type three secretion.
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