VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System.
The Type VI secretion system (T6SS) is widespread among bacterial pathogens and acts as an effective weapon against competitor bacteria and eukaryotic hosts by delivering toxic effector proteins directly into target cells. The T6SS utilises a bacteriophage-like contractile machinery to expel a punct...
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Public Library of Science (PLoS)
2016-06-01
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| Series: | PLoS Pathogens |
| Online Access: | https://journals.plos.org/plospathogens/article/file?id=10.1371/journal.ppat.1005735&type=printable |
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| author | Francesca R Cianfanelli Juliana Alcoforado Diniz Manman Guo Virginia De Cesare Matthias Trost Sarah J Coulthurst |
| author_facet | Francesca R Cianfanelli Juliana Alcoforado Diniz Manman Guo Virginia De Cesare Matthias Trost Sarah J Coulthurst |
| author_sort | Francesca R Cianfanelli |
| collection | DOAJ |
| description | The Type VI secretion system (T6SS) is widespread among bacterial pathogens and acts as an effective weapon against competitor bacteria and eukaryotic hosts by delivering toxic effector proteins directly into target cells. The T6SS utilises a bacteriophage-like contractile machinery to expel a puncturing device based on a tube of Hcp topped with a VgrG spike, which can be extended by a final tip from a PAAR domain-containing protein. Effector proteins are believed to be delivered by specifically associating with particular Hcp, VgrG or PAAR proteins, either covalently ('specialised') or non-covalently ('cargo' effectors). Here we used the T6SS of the opportunistic pathogen Serratia marcescens, together with integratecd genetic, proteomic and biochemical approaches, to elucidate the role of specific VgrG and PAAR homologues in T6SS function and effector specificity, revealing new aspects and unexpected subtleties in effector delivery by the T6SS. We identified effectors, both cargo and specialised, absolutely dependent on a particular VgrG for delivery to target cells, and discovered that other cargo effectors can show a preference for a particular VgrG. The presence of at least one PAAR protein was found to be essential for T6SS function, consistent with designation as a 'core' T6SS component. We showed that specific VgrG-PAAR combinations are required to assemble a functional T6SS and that the three distinct VgrG-PAAR assemblies in S. marcescens exhibit distinct effector specificity and efficiency. Unexpectedly, we discovered that two different PAAR-containing Rhs proteins can functionally pair with the same VgrG protein. Showing that accessory EagR proteins are involved in these interactions, native VgrG-Rhs-EagR complexes were isolated and specific interactions between EagR and cognate Rhs proteins identified. This study defines an essential yet flexible role for PAAR proteins in the T6SS and highlights the existence of distinct versions of the machinery with differential effector specificity and efficiency of target cell delivery. |
| format | Article |
| id | doaj-art-84b3a553f9f54121bfb3db3f0884dabf |
| institution | Kabale University |
| issn | 1553-7366 1553-7374 |
| language | English |
| publishDate | 2016-06-01 |
| publisher | Public Library of Science (PLoS) |
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| series | PLoS Pathogens |
| spelling | doaj-art-84b3a553f9f54121bfb3db3f0884dabf2025-08-20T03:26:16ZengPublic Library of Science (PLoS)PLoS Pathogens1553-73661553-73742016-06-01126e100573510.1371/journal.ppat.1005735VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System.Francesca R CianfanelliJuliana Alcoforado DinizManman GuoVirginia De CesareMatthias TrostSarah J CoulthurstThe Type VI secretion system (T6SS) is widespread among bacterial pathogens and acts as an effective weapon against competitor bacteria and eukaryotic hosts by delivering toxic effector proteins directly into target cells. The T6SS utilises a bacteriophage-like contractile machinery to expel a puncturing device based on a tube of Hcp topped with a VgrG spike, which can be extended by a final tip from a PAAR domain-containing protein. Effector proteins are believed to be delivered by specifically associating with particular Hcp, VgrG or PAAR proteins, either covalently ('specialised') or non-covalently ('cargo' effectors). Here we used the T6SS of the opportunistic pathogen Serratia marcescens, together with integratecd genetic, proteomic and biochemical approaches, to elucidate the role of specific VgrG and PAAR homologues in T6SS function and effector specificity, revealing new aspects and unexpected subtleties in effector delivery by the T6SS. We identified effectors, both cargo and specialised, absolutely dependent on a particular VgrG for delivery to target cells, and discovered that other cargo effectors can show a preference for a particular VgrG. The presence of at least one PAAR protein was found to be essential for T6SS function, consistent with designation as a 'core' T6SS component. We showed that specific VgrG-PAAR combinations are required to assemble a functional T6SS and that the three distinct VgrG-PAAR assemblies in S. marcescens exhibit distinct effector specificity and efficiency. Unexpectedly, we discovered that two different PAAR-containing Rhs proteins can functionally pair with the same VgrG protein. Showing that accessory EagR proteins are involved in these interactions, native VgrG-Rhs-EagR complexes were isolated and specific interactions between EagR and cognate Rhs proteins identified. This study defines an essential yet flexible role for PAAR proteins in the T6SS and highlights the existence of distinct versions of the machinery with differential effector specificity and efficiency of target cell delivery.https://journals.plos.org/plospathogens/article/file?id=10.1371/journal.ppat.1005735&type=printable |
| spellingShingle | Francesca R Cianfanelli Juliana Alcoforado Diniz Manman Guo Virginia De Cesare Matthias Trost Sarah J Coulthurst VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. PLoS Pathogens |
| title | VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. |
| title_full | VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. |
| title_fullStr | VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. |
| title_full_unstemmed | VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. |
| title_short | VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. |
| title_sort | vgrg and paar proteins define distinct versions of a functional type vi secretion system |
| url | https://journals.plos.org/plospathogens/article/file?id=10.1371/journal.ppat.1005735&type=printable |
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