scholarly journals Critical Role of a Sheath Phosphorylation Site On the Assembly and Function of an Atypical Type VI Secretion System

2019 ◽  
Vol 18 (12) ◽  
pp. 2418-2432 ◽  
Author(s):  
Jason Ziveri ◽  
Cerina Chhuon ◽  
Anne Jamet ◽  
Héloïse Rytter ◽  
Guénolé Prigent ◽  
...  
Keyword(s):  
Critical Role ◽  
Phosphorylation Site ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Type Vi Secretion ◽  
And Function

scholarly journals Extended Loop Region of Hcp1 is Critical for the Assembly and Function of Type VI Secretion System in Burkholderia pseudomallei

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Yan Ting Lim ◽  
Chacko Jobichen ◽  
Jocelyn Wong ◽  
Direk Limmathurotsakul ◽  
Shaowei Li ◽  
...  
Keyword(s):  
Burkholderia Pseudomallei ◽  
Secretion System ◽  
Type Vi Secretion System ◽  
Loop Region ◽  
Type Vi Secretion ◽  
And Function

scholarly journals A proline-rich sequence unique to MEK1 and MEK2 is required for raf binding and regulates MEK function.

1995 ◽  
Vol 15 (10) ◽  
pp. 5214-5225 ◽  
Author(s):  
A D Catling ◽  
H J Schaeffer ◽  
C W Reuter ◽  
G R Reddy ◽  
M J Weber
Keyword(s):  
Protein Interactions ◽  
Critical Role ◽  
Phosphorylation Site ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Serum Stimulation ◽  
And Function

Mammalian MEK1 and MEK2 contain a proline-rich (PR) sequence that is absent both from the yeast homologs Ste7 and Byr1 and from a recently cloned activator of the JNK/stress-activated protein kinases, SEK1/MKK4. Since this PR sequence occurs in MEKs that are regulated by Raf family enzymes but is missing from MEKs and SEKs activated independently of Raf, we sought to investigate the role of this sequence in MEK1 and MEK2 regulation and function. Deletion of the PR sequence from MEK1 blocked the ability of MEK1 to associate with members of the Raf family and markedly attenuated activation of the protein in vivo following growth factor stimulation. In addition, this sequence was necessary for efficient activation of MEK1 in vitro by B-Raf but dispensable for activation by a novel MEK1 activator which we have previously detected in fractionated fibroblast extracts. Furthermore, we found that a phosphorylation site within the PR sequence of MEK1 was required for sustained MEK1 activity in response to serum stimulation of quiescent fibroblasts. Consistent with this observation, we observed that MEK2, which lacks a phosphorylation site at the corresponding position, was activated only transiently following serum stimulation. Finally, we found that deletion of the PR sequence from a constitutively activated MEK1 mutant rendered the protein nontransforming in Rat1 fibroblasts. These observations indicate a critical role for the PR sequence in directing specific protein-protein interactions important for the activation, inactivation, and downstream functioning of the MEKs.

scholarly journals Beyond dueling: roles of the type VI secretion system in microbiome modulation, pathogenesis and stress resistance

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Jinshui Lin ◽  
Lei Xu ◽  
Jianshe Yang ◽  
Zhuo Wang ◽  
Xihui Shen
Keyword(s):  
Stress Resistance ◽  
Secretion System ◽  
Bacterial Cells ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Competitive Fitness ◽  
Type Vi Secretion ◽  
Protein Secretion Systems ◽  
Extracellular Environment

AbstractBacteria inhabit diverse and dynamic environments, where nutrients may be limited and toxic chemicals can be prevalent. To adapt to these stressful conditions, bacteria have evolved specialized protein secretion systems, such as the type VI secretion system (T6SS) to facilitate their survival. As a molecular syringe, the T6SS expels various effectors into neighboring bacterial cells, eukaryotic cells, or the extracellular environment. These effectors improve the competitive fitness and environmental adaption of bacterial cells. Although primarily recognized as antibacterial weapons, recent studies have demonstrated that T6SSs have functions beyond interspecies competition. Here, we summarize recent research on the role of T6SSs in microbiome modulation, pathogenesis, and stress resistance.

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

2021 ◽  
Vol 17 (12) ◽  
pp. e1010116
Author(s):  
Xiaoye Liang ◽  
Tong-Tong Pei ◽  
Hao Li ◽  
Hao-Yu Zheng ◽  
Han Luo ◽  
...  
Keyword(s):  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Structural Proteins ◽  
Wild Type ◽  
Type Vi Secretion System ◽  
Double Deletion ◽  
Type Vi Secretion ◽  
Structural Determinant

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.

scholarly journals A post-translational modification of the sheath modulatesFrancisellatype VI secretion system assembly and function

2018 ◽  
Author(s):  
Jason Ziveri ◽  
Cerina Chhuon ◽  
Anne Jamet ◽  
Guénolé Prigent ◽  
Héloïse Rytter ◽  
...  
Keyword(s):  
Critical Role ◽  
Phosphorylation Site ◽  
Post Translational Modification ◽  
Secretion Systems ◽  
Post Translational Modifications ◽  
Type Vi Secretion ◽  
Sheath Formation ◽  
Canonical Type ◽  
The Stability ◽  
And Function

AbstractFrancisella tularensisis a facultative intracellular pathogen that causes the zoonotic disease tularemia in human and animal hosts. This bacterium possesses a non-canonical type VI secretion systems (T6SS) required for phagosomal escape and access to its replicative niche in the cytosol of infected macrophages. KCl stimulation has been previously used to trigger assembly and secretion of the Francisella T6SS in culture. We found that the amounts of essentially all the TSS6 proteins remained unchanged upon KCl stimulation. We therefore hypothesized that a post-translational modification might be involved in T6SS assembly. A whole cell phosphoproteomic analysis allowed us to identify a unique phosphorylation site on IglB, the TssC homologue and key component of the T6SS sheath. Importantly, the phosphorylated form of IglB was not present in the contracted sheath and 3D modeling indicated that the charge repulsion provoked by addition of a phosphogroup on tyrosine 139 was likely to weaken the stability of the sheath structure. Substitutions of the phosphorylatable residue of IglB (tyrosine 139) with alanine or with phosphomimetics prevented T6SS formation and totally impaired phagosomal escape. In contrast, the substitution with the non-phosphorylatable aromatic analog phenylalanine impaired but did not prevent phagosomal escape and cytosolic bacterial multiplication in J774-1 macrophages. Altogether these data suggest that phosphorylation of the sheath participates to T6SS disassembly. Post-translational modifications of the sheath may represent a previously unrecognized mechanism to finely modulate the dynamics of T6SS assembly-disassembly.Data are available via ProteomeXchange with identifier PXD012507.SynopsisFrancisellapossesses a non-canonical T6SS that is essential for efficient phagosomal escape and access to the cytosol of infected macrophages. KCl stimulation has been previously used to trigger assembly and secretion of the Francisella T6SS in culture. We found that KCl stimulation did not result in an increased production of TSS6 proteins. We therefore hypothesized that a post-translational modification might be involved in T6SS assembly. Using a global and site-specific phosphoproteomic analysis ofFrancisellawe identified a unique phosphorylation site on IglB, the TssC homologue and a key component of the T6SS contractile sheath. We show that this site plays a critical role in T6SS biogenesis and propose that phosphorylation may represent a new mechanism affecting the dynamics of sheath formation.

scholarly journals The Type VI Secretion System: A Multipurpose Delivery System with a Phage-Like Machinery

2011 ◽  
Vol 24 (7) ◽  
pp. 751-757 ◽  
Author(s):  
Angela R. Records
Keyword(s):  
Plant Growth Promoting Rhizobacteria ◽  
Secretion System ◽  
Host Cells ◽  
Type Vi Secretion System ◽  
Secretion Systems ◽  
Gram Negative ◽  
Extracellular Milieu ◽  
Type Vi Secretion ◽  
Plant Growth Promoting ◽  
And Function

Whether they live in the soil, drift in the ocean, survive in the lungs of human hosts or reside on the surfaces of leaves, all bacteria must cope with an array of environmental stressors. Bacteria have evolved an impressive suite of protein secretion systems that enable their survival in hostile environments and facilitate colonization of eukaryotic hosts. Collectively, gram-negative bacteria produce six distinct secretion systems that deliver proteins to the extracellular milieu or directly into the cytosol of host cells. The type VI secretion system (T6SS) was discovered recently and is encoded in at least one fourth of all sequenced gram-negative bacterial genomes. T6SS proteins are evolutionarily and structurally related to phage proteins, and it is likely that the T6SS apparatus is reminiscent of phage injection machinery. Most studies of T6SS function have been conducted in the context of host-pathogen interactions. However, the totality of data suggests that the T6SS is a versatile tool with roles in virulence, symbiosis, interbacterial interactions, and antipathogenesis. This review gives a brief history of T6SS discovery and an overview of the pathway's predicted structure and function. Special attention is paid to research addressing the T6SS of plant-associated bacteria, including pathogens, symbionts and plant growth–promoting rhizobacteria.

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