Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Type VI secretion system sheath inter-subunit interactions modulate its contraction.

ABSTRACT: Secretion systems are essential for bacteria to survive and manipulate their environment. The bacterial type VI secretion system (T6SS) generates the force needed for protein translocation by the contraction of a long polymer called sheath. The sheath is a six-start helical assembly of interconnected VipA/VipB subunits. The mechanism of T6SS sheath contraction is unknown. Here, we show that elongating the N-terminal VipA linker or eliminating charge of a specific VipB residue abolishes sheath contraction and delivery of effectors into target cells. Mass spectrometry analysis identified the inner tube protein Hcp, spike protein VgrG, and other components of the T6SS baseplate significantly enriched in samples of the stable non-contractile sheaths. The ability to lock the T6SS in the pre-firing state opens new possibilities for understanding its mode of action.

SUBMITTER: Brackmann M

PROVIDER: S-EPMC5797969 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Type VI secretion system sheath inter-subunit interactions modulate its contraction.

Brackmann Maximilian M Wang Jing J Basler Marek M

EMBO reports 20171208 2

Secretion systems are essential for bacteria to survive and manipulate their environment. The bacterial type VI secretion system (T6SS) generates the force needed for protein translocation by the contraction of a long polymer called sheath. The sheath is a six-start helical assembly of interconnected VipA/VipB subunits. The mechanism of T6SS sheath contraction is unknown. Here, we show that elongating the N-terminal VipA linker or eliminating charge of a specific VipB residue abolishes sheath co ...[more]

PMID: 29222345

Similar Datasets

Structure of the type VI secretion system contractile sheath.

Project description:Bacteria use rapid contraction of a long sheath of the type VI secretion system (T6SS) to deliver effectors into a target cell. Here, we present an atomic-resolution structure of a native contracted Vibrio cholerae sheath determined by cryo-electron microscopy. The sheath subunits, composed of tightly interacting proteins VipA and VipB, assemble into a six-start helix. The helix is stabilized by a core domain assembled from four β strands donated by one VipA and two VipB molecules. The fold of inner and middle layers is conserved between T6SS and phage sheaths. However, the structure of the outer layer is distinct and suggests a mechanism of interaction of the bacterial sheath with an accessory ATPase, ClpV, that facilitates multiple rounds of effector delivery. Our results provide a mechanistic insight into assembly of contractile nanomachines that bacteria and phages use to translocate macromolecules across membranes.

| S-EPMC4359589 | biostudies-literature

A novel stabilization mechanism for the type VI secretion system sheath.

Project description:The type VI secretion system (T6SS) is a phage-derived contractile nanomachine primarily involved in interbacterial competition. Its pivotal component, TssA, is indispensable for the assembly of the T6SS sheath structure, the contraction of which propels a payload of effector proteins into neighboring cells. Despite their key function, TssA proteins exhibit unexpected diversity and exist in two major forms, a short form (TssAS) and a long form (TssAL). While TssAL proteins interact with a partner, called TagA, to anchor the distal end of the extended sheath, the mechanism for the stabilization of TssAS-containing T6SSs remains unknown. Here we discover a class of structural components that interact with short TssA proteins and contribute to T6SS assembly by stabilizing the polymerizing sheath from the baseplate. We demonstrate that the presence of these components is important for full sheath extension and optimal firing. Moreover, we show that the pairing of each form of TssA with a different class of sheath stabilization proteins results in T6SS apparatuses that either reside in the cell for some time or fire immediately after sheath extension. We propose that this diversity in firing dynamics could contribute to the specialization of the T6SS to suit bacterial lifestyles in diverse environmental niches.

| S-EPMC7896307 | biostudies-literature

Cryo-EM reconstruction of Type VI secretion system baseplate and sheath distal end.

Project description:The bacterial Type VI secretion system (T6SS) assembles from three major parts: a membrane complex that spans inner and outer membranes, a baseplate, and a sheath-tube polymer. The baseplate assembles around a tip complex with associated effectors and connects to the membrane complex by TssK. The baseplate assembly initiates sheath-tube polymerization, which in some organisms requires TssA. Here, we analyzed both ends of isolated non-contractile Vibrio cholerae sheaths by cryo-electron microscopy. Our analysis suggests that the baseplate, solved to an average 8.0 Å resolution, is composed of six subunits of TssE/F2/G and the baseplate periphery is decorated by six TssK trimers. The VgrG/PAAR tip complex in the center of the baseplate is surrounded by a cavity, which may accommodate up to ~450 kDa of effector proteins. The distal end of the sheath, resolved to an average 7.5 Å resolution, shows sixfold symmetry; however, its protein composition is unclear. Our structures provide an important step toward an atomic model of the complete T6SS assembly.

| S-EPMC5813253 | biostudies-literature

Cryo EM of Type VI Secretion System VipA-N2/VipB contracted sheath

Project description: Not available

| EMPIAR-10085 | biostudies-other

The type VI secretion system sheath assembles at the end distal from the membrane anchor.

Project description:The bacterial Type VI secretion system (T6SS) delivers proteins into target cells using fast contraction of a long sheath anchored to the cell envelope and wrapped around an inner Hcp tube associated with the secreted proteins. Mechanisms of sheath assembly and length regulation are unclear. Here we study these processes using spheroplasts formed from ampicillin-treated Vibrio cholerae. We show that spheroplasts secrete Hcp and deliver T6SS substrates into neighbouring cells. Imaging of sheath dynamics shows that the sheath length correlates with the diameter of spheroplasts and may reach up to several micrometres. Analysis of sheath assembly after partial photobleaching shows that subunits are exclusively added to the sheath at the end that is distal from the baseplate and cell envelope attachment. We suggest that this mode of assembly is likely common for all phage-like contractile nanomachines, because of the conservation of the structures and connectivity of sheath subunits.

| S-EPMC5511345 | biostudies-literature

TssA-TssM-TagA interaction modulates type VI secretion system sheath-tube assembly in Vibrio cholerae.

Project description:The type VI protein secretion system (T6SS) is a powerful needle-like machinery found in Gram-negative bacteria that can penetrate the cytosol of receiving cells in milliseconds by physical force. Anchored by its membrane-spanning complex (MC) and a baseplate (BP), the T6SS sheath-tube is assembled in a stepwise process primed by TssA and terminated by TagA. However, the molecular details of its assembly remain elusive. Here, we systematically examined the initiation and termination of contractile and non-contractile T6SS sheaths in MC-BP, tssA and tagA mutants by fluorescence microscopy. We observe long pole-to-pole sheath-tube structures in the non-contractile MC-BP defective mutants but not in the Hcp tube or VgrG spike mutants. Combining overexpression and genetic mutation data, we demonstrate complex effects of TssM, TssA and TagA interactions on T6SS sheath-tube dynamics. We also report promiscuous interactions of TagA with multiple T6SS components, similar to TssA. Our results demonstrate that priming of the T6SS sheath-tube assembly is not dependent on TssA, nor is the assembly termination dependent on the distal end TssA-TagA interaction, and highlight the tripartite control of TssA-TssM-TagA on sheath-tube initiation and termination.

| S-EPMC7545191 | biostudies-literature

VgrG-dependent effectors and chaperones modulate the assembly of the type VI secretion system.

Project description:The type VI secretion system (T6SS) is a spear-like nanomachine found in gram-negative pathogens for delivery of toxic effectors to neighboring bacterial and host cells. Its assembly requires a tip spike complex consisting of a VgrG-trimer, a PAAR protein, and the interacting effectors. However, how the spike controls T6SS assembly remains elusive. Here we investigated the role of three VgrG-effector pairs in Aeromonas dhakensis strain SSU, a clinical isolate with a constitutively active T6SS. By swapping VgrG tail sequences, we demonstrate that the C-terminal ~30 amino-acid tail dictates effector specificity. Double deletion of vgrG1&2 genes (VgrG3+) abolished T6SS secretion, which can be rescued by ectopically expressing chimeric VgrG3 with a VgrG1/2-tail but not the wild type VgrG3. In addition, deletion of effector-specific chaperones also severely impaired T6SS secretion, despite the presence of intact VgrG and effector proteins, in both SSU and Vibrio cholerae V52. We further show that SSU could deliver a V. cholerae effector VasX when expressing a plasmid-borne chimeric VgrG with VasX-specific VgrG tail and chaperone sequences. Pull-down analyses show that two SSU effectors, TseP and TseC, could interact with their cognate VgrGs, the baseplate protein TssK, and the key assembly chaperone TssA. Effectors TseL and VasX could interact with TssF, TssK and TssA in V. cholerae. Collectively, we demonstrate that chimeric VgrG-effector pairs could bypass the requirement of heterologous VgrG complex and propose that effector-stuffing inside the baseplate complex, facilitated by chaperones and the interaction with structural proteins, serves as a crucial structural determinant for T6SS assembly.

| S-EPMC8668125 | biostudies-literature

Bile Salts Modulate the Mucin-Activated Type VI Secretion System of Pandemic Vibrio cholerae.

Project description:The causative agent of cholera, Vibrio cholerae, regulates its diverse virulence factors to thrive in the human small intestine and environmental reservoirs. Among this pathogen's arsenal of virulence factors is the tightly regulated type VI secretion system (T6SS). This system acts as an inverted bacteriophage to inject toxins into competing bacteria and eukaryotic phagocytes. V. cholerae strains responsible for the current 7th pandemic activate their T6SS within the host. We established that T6SS-mediated competition occurs upon T6SS activation in the infant mouse, and that this system is functional under anaerobic conditions. When investigating the intestinal host factors mucins (a glycoprotein component of mucus) and bile for potential regulatory roles in controlling the T6SS, we discovered that once mucins activate the T6SS, bile acids can further modulate T6SS activity. Microbiota modify bile acids to inhibit T6SS-mediated killing of commensal bacteria. This interplay is a novel interaction between commensal bacteria, host factors, and the V. cholerae T6SS, showing an active host role in infection.

| S-EPMC4552747 | biostudies-literature

The Francisella Type VI Secretion System.

Project description:Francisella tularensisis subsp. tularensis is an intracellular bacterial pathogen and the causative agent of the life-threatening zoonotic disease tularemia. The Francisella Pathogenicity Island encodes a large secretion apparatus, known as a Type VI Secretion System (T6SS), which is essential for Francisella to escape from its phagosome and multiply within host macrophages and to cause disease in animals. The T6SS, found in one-quarter of Gram-negative bacteria including many highly pathogenic ones, is a recently discovered secretion system that is not yet fully understood. Nevertheless, there have been remarkable advances in our understanding of the structure, composition, and function of T6SSs of several bacteria in the past few years. The system operates like an inside-out headless contractile phage that is anchored to the bacterial membrane via a baseplate and membrane complex. The system injects effector molecules across the inner and outer bacterial membrane and into host prokaryotic or eukaryotic targets to kill, intoxicate, or in the case of Francisella, hijack the target cell. Recent advances include an atomic model of the contractile sheath, insights into the mechanics of sheath contraction, the composition of the baseplate and membrane complex, the process of assembly of the apparatus, and identification of numerous effector molecules and activities. While Francisella T6SS appears to be an outlier among T6SSs, with limited or no sequence homology with other systems, its structure and organization are strikingly similar to other systems. Nevertheless, we have only scratched the surface in uncovering the mysteries of the Francisella T6SS, and there are numerous questions that remain to be answered.

| S-EPMC5924787 | biostudies-literature

Marker for type VI secretion system effectors.

Project description:Bacteria use diverse mechanisms to kill, manipulate, and compete with other cells. The recently discovered type VI secretion system (T6SS) is widespread in bacterial pathogens and used to deliver virulence effector proteins into target cells. Using comparative proteomics, we identified two previously unidentified T6SS effectors that contained a conserved motif. Bioinformatic analyses revealed that this N-terminal motif, named MIX (marker for type six effectors), is found in numerous polymorphic bacterial proteins that are primarily located in the T6SS genome neighborhood. We demonstrate that several MIX-containing proteins are T6SS effectors and that they are not required for T6SS activity. Thus, we propose that MIX-containing proteins are T6SS effectors. Our findings allow for the identification of numerous uncharacterized T6SS effectors that will undoubtedly lead to the discovery of new biological mechanisms.

| S-EPMC4078801 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data