A protein secreted by the Salmonella type III secretion system controls needle filament assembly

Abstract
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Abstract

Type III protein secretion systems (T3SS) are encoded by several pathogenic or symbiotic bacteria. The central component of this nanomachine is the needle complex. Here we show in a Salmonella Typhimurium T3SS that assembly of the needle filament of this structure requires OrgC, a protein encoded within the T3SS gene cluster. Absence of OrgC results in significantly reduced number of needle substructures but does not affect needle length. We show that OrgC is secreted by the T3SS and that exogenous addition of OrgC can complement a ∆orgC mutation. We also show that OrgC interacts with the needle filament subunit PrgI and accelerates its polymerization into filaments in vitro. The structure of OrgC shows a novel fold with a shared topology with a domain from flagellar capping proteins. These findings identify a novel component of T3SS and provide new insight into the assembly of the type III secretion machine.

Data availability

The 20 PDB coordinates, the assigned chemical shifts, and the restraints used in the NMR structure determination were deposited at the RCSB Protein Data Bank with the accession code PDB ID 6CJD and BMRB ID 30417. The above data were used to generate Fig. 7, Figure 6-figure supplement 1, Figure 7-figure supplement 1, 2, 3, and 4, and Supplementary File 1.

The following data sets were generated

1. Kato J
2. Dey S
3. Soto JE
4. Butan C
5. Wilkinson MC
6. De Guzman RN
7. Galán JE
(2018) NMR NMR structure determination of OrgC
Publicly available at the RCSB Protein Data Bank (accession no. 6CJD).

https://www.rcsb.org/
1. Kato J
2. Dey S
3. Soto JE
4. Butan C
5. Wilkinson MC
6. De Guzman RN
7. Galán JE
(2018) NMR NMR structure determination of OrgC
30417.

https://www.rcsb.org/

Article and author information

Author details

Junya Kato

Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, United States

Competing interests
The authors declare that no competing interests exist.
Supratim Dey

Department of Molecular Biosciences, University of Kansas, Lawrence, United States

Competing interests
The authors declare that no competing interests exist.
Jose E Soto

Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, United States

Competing interests
The authors declare that no competing interests exist.
Carmen Butan

Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, United States

Competing interests
The authors declare that no competing interests exist.
Mason C Wilkinson

Department of Molecular Biosciences, University of Kansas, Lawrence, United States

Competing interests
The authors declare that no competing interests exist.
Roberto N De Guzman

Department of Molecular Biosciences, University of Kansas, Lawrence, United States

For correspondence
rdguzman@ku.edu

Competing interests
The authors declare that no competing interests exist.
Jorge E Galan

Department of Microbial Pathogenesis, Yale University School of Medicine, New haven, United States

For correspondence
jorge.galan@yale.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-6531-0355

Funding

National Institutes of Health (AI079022)

Jorge E Galan

National Institutes of Health (AI074856)

Roberto N De Guzman

National Institutes of Health (P20GM103418)

Mason C Wilkinson

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.