The type III secretion injectisome, a complex nanomachine for intracellular ‘toxin’ delivery

Cornelis, Guy R.

doi:10.1515/bc.2010.079

Cited by 108 publications

(101 citation statements)

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“…The T3SS is an essential virulence system that translocates bacterial effector proteins into host cells to alter normal cell functions for the benefit of the pathogen. 3,4 Many important pathogens employ T3SSs as virulence mechanisms and while there are distinct pathogen-specific differences in T3SS effector functions, the Type III secretion apparatus (T3SA) maintains significant structural homology across diverse species boundaries. 3 In all cases, the T3SA is anchored in the bacterial envelope by a basal body, which supports an external needle composed of many copies of a small, polymerized needle protein terminating at a needle tip complex that contributes to secretion control.…”

Section: Introductionmentioning

confidence: 99%

Oligomeric states of the Shigella translocator protein IpaB provide structural insights into formation of the type III secretion translocon

et al. 2013

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The Shigella flexneri Type III secretion system (T3SS) senses contact with human intestinal cells and injects effector proteins that promote pathogen entry as the first step in causing life threatening bacillary dysentery (shigellosis). The Shigella Type III secretion apparatus (T3SA) consists of an anchoring basal body, an exposed needle, and a temporally assembled tip complex. Exposure to environmental small molecules recruits IpaB, the first hydrophobic translocator protein, to the maturing tip complex. IpaB then senses contact with a host cell membrane, forming the translocon pore through which effectors are delivered to the host cytoplasm. Within the bacterium, IpaB exists as a heterodimer with its chaperone IpgC; however, IpaB's structural state following secretion is unknown due to difficulties isolating stable protein.We have overcome this by coexpressing the IpaB/IpgC heterodimer and isolating IpaB by incubating the complex in mild detergents. Interestingly, preparation of IpaB with n-octyl-oligooxyethylene (OPOE) results in the assembly of discrete oligomers while purification in N,Ndimethyldodecylamine N-oxide (LDAO) maintains IpaB as a monomer. In this study, we demonstrate that IpaB tetramers penetrate phospholipid membranes to allow a size-dependent release of small molecules, suggesting the formation of discrete pores. Monomeric IpaB also interacts with liposomes but fails to disrupt them. From these and additional findings, we propose Abbreviations: AUC, analytical ultracentrifugation; CD, circular dichroism; CMC, critical micelle concentration; DGS-NTA, 1,2-dioleoylsn-glycero-3-[(N-(5-amino-1-carboxypentyl) iminodiacetic acid)succinyl]; DLS, dynamic light scattering; DMSO, dimethyl sulfoxide; DOPC, dioleoylphosphatidylcholine; DOPG, dioleoylphosphatidylglycerol; DSP, dithiobis[succinimidyl proprionate; FM, fluorescein maleimide; FRET, F-rster resonance energy transfer; Ipa, invasion plasmid antigen; Ipg, invasion plasmid gene; LDAO, N,N-dimethyldodecylamine N-oxide; Mxi, major exporter of Ipas; OPOE, n-Octyl-oligo-oxyethylene; SATA, N-succinimidyl-S-acetylthioacetate; SEC, size exclusion chromatography; SRB, sulforhodamine B; T m , thermal unfolding midpoint; TCEP, (tris (2-carboxyethyl)phosphine; TRITC DHPE, (N-(6-tetramethylrhodaminethiocarbamoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine); T3SS, type-III secretion system; T3SA, type III secretion apparatus.Additional Supporting Information may be found in the online version of this article. that IpaB can exist as a tetramer having inherent flexibility, which allows it to cooperatively interact with and insert into host cell membranes. This event may then lay the foundation for formation of the Shigella T3SS translocon pore.

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Section: Introductionmentioning

confidence: 99%

Oligomeric states of the Shigella translocator protein IpaB provide structural insights into formation of the type III secretion translocon

et al. 2013

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“…The aim of this review is to summarize our current knowledge of the architecture of T3S systems and the control mechanisms underlying T3S in plant-and animal-pathogenic bacteria. For a detailed description of individual proteins or regulatory mechanisms, the reader is also referred to excellent previous overview articles that provide summaries on the following topics: translocation-associated T3S systems (29,72,105,161,199,217,557), flagellar T3S systems (92,161,343,377,428,549), T3S chaperones (175,431), structures and functions of individual components of T3S systems (46,70,243,281,283,349,353,389,395,482), and control mechanisms underlying T3S and gene expression (64,106,129,212,370,421,547,555,588).…”

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confidence: 99%

Protein Export According to Schedule: Architecture, Assembly, and Regulation of Type III Secretion Systems from Plant- and Animal-Pathogenic Bacteria

Büttner

2012

Microbiol Mol Biol Rev

359

482

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SUMMARY Flagellar and translocation-associated type III secretion (T3S) systems are present in most Gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.

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“…bacterial nanomachines | protein secretion | superresolution microscopy | bacterial pathogenesis | Salmonella virulence T ype III secretion systems are remarkable molecular machines with the capacity to inject multiple bacterial proteins into eukaryotic cells (1,2). These machines play an essential role in the pathogenic or symbiotic relationships between the bacteria that encode them and their respective hosts.…”

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confidence: 99%

Visualization and characterization of individual type III protein secretion machines in live bacteria

Zhang

Lara‐Tejero

Bewersdorf

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

103

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Type III protein secretion machines have evolved to deliver bacterially encoded effector proteins into eukaryotic cells. Although electron microscopy has provided a detailed view of these machines in isolation or fixed samples, little is known about their organization in live bacteria. Here we report the visualization and characterization of the Salmonella type III secretion machine in live bacteria by 2D and 3D single-molecule switching superresolution microscopy. This approach provided access to transient components of this machine, which previously could not be analyzed. We determined the subcellular distribution of individual machines, the stoichiometry of the different components of this machine in situ, and the spatial distribution of the substrates of this machine before secretion. Furthermore, by visualizing this machine in Salmonella mutants we obtained major insights into the machine's assembly. This study bridges a major resolution gap in the visualization of this nanomachine and may serve as a paradigm for the examination of other bacterially encoded molecular machines.bacterial nanomachines | protein secretion | superresolution microscopy | bacterial pathogenesis | Salmonella virulence T ype III secretion systems are remarkable molecular machines with the capacity to inject multiple bacterial proteins into eukaryotic cells (1, 2). These machines play an essential role in the pathogenic or symbiotic relationships between the bacteria that encode them and their respective hosts. Consequently, type III secretion systems are rapidly emerging as targets for the development of novel therapeutic and prevention strategies with the potential to combat several important infectious diseases (3-5). The components of type III secretion machines are highly conserved across bacterial species although the effector proteins that they deliver are customized for the specific bacteria that harbor them (1, 6, 7). The entire type III secretion machine or injectisome is ∼40 nm in width and ∼150 nm in length and is organized in defined substructures (Fig. 1A). The bestcharacterized substructure is the needle complex, which is a multi-ring cylindrical structure embedded in the bacterial envelope with a needle-like extension that projects several nanometers from the bacterial surface. The needle complex is traversed by a narrow channel that serves as the conduit for the proteins that travel this secretion pathway (8). The needle is capped at its end by the tip complex, which is thought to coordinate the activation of the secretion machine upon contact with target cells (9, 10). Because the needle complex can be isolated in a manner suitable for single-particle cryo-electron microscopy, its organization at the quasi-atomic level is known (11-18). Passage of the secreted proteins through the inner membrane requires the export apparatus, which is composed of a group of poly-topic inner membrane proteins located at the center of the needle complex base (19). Finally, several cytoplasmic proteins form a large complex known as the...

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The type III secretion injectisome, a complex nanomachine for intracellular ‘toxin’ delivery

Cited by 108 publications

References 92 publications

Oligomeric states of the Shigella translocator protein IpaB provide structural insights into formation of the type III secretion translocon

Oligomeric states of the Shigella translocator protein IpaB provide structural insights into formation of the type III secretion translocon

Protein Export According to Schedule: Architecture, Assembly, and Regulation of Type III Secretion Systems from Plant- and Animal-Pathogenic Bacteria

Visualization and characterization of individual type III protein secretion machines in live bacteria

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