A common assembly module in injectisome and flagellar type III secretion sorting platforms
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Updated: Apr 12, 2026

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking
Published on: December 17, 2013
Ryan Q Notti1, Shibani Bhattacharya2, Mirjana Lilic3
11] Laboratory of Structural Microbiology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA [2] Tri-Institutional Medical Scientist Training Program, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10021, USA.
Abstract:
Translocating proteins across the double membrane of Gram-negative bacteria, type III secretion systems (T3SS) occur in two evolutionarily related forms: injectisomes, delivering virulence factors into host cells, and the flagellar system, secreting the polymeric filament used for motility. While both systems share related elements of a cytoplasmic sorting platform that facilitates the hierarchical secretion of protein substrates, its assembly and regulation remain unclear. Here we describe a module mediating the assembly of the sorting platform in both secretion systems, and elucidate the structural basis for segregation of homologous components among these divergent T3SS subtypes sharing a common cytoplasmic milieu. These results provide a foundation for the subtype-specific assembly of T3SS sorting platforms and will support further mechanistic analysis and anti-virulence drug design.
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