EMD-20831
Cryo-EM reconstruction shows that the needle complex's inner rings from Salmonella assemble with 23-fold symmetry in the absence of the export apparatus.
EMD-20831
Single-particle5.3 Å
Deposition: 15/10/2019Map released: 01/07/2020
Last modified: 01/07/2020
Sample Organism:
Salmonella enterica subsp. enterica serovar Typhimurium
Sample: Complex of PrgH and PrgK, the protein components of the inner rings of Salmonella's needle complex, assembled in the absence of the export apparatus.
Deposition Authors: Butan C, Galan J
Sample: Complex of PrgH and PrgK, the protein components of the inner rings of Salmonella's needle complex, assembled in the absence of the export apparatus.
Deposition Authors: Butan C, Galan J
High-resolution view of the type III secretion export apparatus in situ reveals membrane remodeling and a secretion pathway.
Abstract:
Type III protein secretion systems are essential virulence factors for many important pathogenic bacteria. The entire protein secretion machine is composed of several substructures that organize into a holostructure or injectisome. The core component of the injectisome is the needle complex, which houses the export apparatus that serves as a gate for the passage of the secreted proteins through the bacterial inner membrane. Here, we describe a high-resolution structure of the export apparatus of the Salmonella type III secretion system in association with the needle complex and the underlying bacterial membrane, both in isolation and in situ. We show the precise location of the core export apparatus components within the injectisome and bacterial envelope and demonstrate that their deployment results in major membrane remodeling and thinning, which may be central for the protein translocation process. We also show that InvA, a critical export apparatus component, forms a multiring cytoplasmic conduit that provides a pathway for the type III secretion substrates to reach the entrance of the export gate. Combined with structure-guided mutagenesis, our studies provide major insight into potential mechanisms of protein translocation and injectisome assembly.
Type III protein secretion systems are essential virulence factors for many important pathogenic bacteria. The entire protein secretion machine is composed of several substructures that organize into a holostructure or injectisome. The core component of the injectisome is the needle complex, which houses the export apparatus that serves as a gate for the passage of the secreted proteins through the bacterial inner membrane. Here, we describe a high-resolution structure of the export apparatus of the Salmonella type III secretion system in association with the needle complex and the underlying bacterial membrane, both in isolation and in situ. We show the precise location of the core export apparatus components within the injectisome and bacterial envelope and demonstrate that their deployment results in major membrane remodeling and thinning, which may be central for the protein translocation process. We also show that InvA, a critical export apparatus component, forms a multiring cytoplasmic conduit that provides a pathway for the type III secretion substrates to reach the entrance of the export gate. Combined with structure-guided mutagenesis, our studies provide major insight into potential mechanisms of protein translocation and injectisome assembly.