VgrG1c (PA2685, originally called VgrG4) is a valine-glycine repeat G (VgrG) spike protein of the H1 type VI secretion system (H1-T6SS) of Pseudomonas aeruginosa. Its gene lies outside the HSI-I cluster but is co-regulated with it through the RetS/Gac-Rsm pathway. VgrG1c forms homomultimers, is exported by the H1-T6SS in a ClpV1-dependent manner, and is required, redundantly with VgrG1a, for secretion of Hcp1; VgrG proteins are also needed for export of other H1-T6SS substrates, and VgrG1c carries a specific subset of them (the Rhs protein RhsP1/Tse5).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005576 extracellular region | EXP PMID:21325275 Type VI secretion system in Pseudomonas aeruginosa: secretio... | KEEP AS NON CORE | Summary: VgrG1c is recovered from culture supernatants in a ClpV1-dependent manner. Reason: Correct but peripheral: the spike is exported when the system fires. The functional location is the assembled apparatus. Supporting Evidence: PMID:21325275 Whereas VgrG1a and VgrG1c were secreted in a ClpV1-dependent manner, secretion of VgrG1b was ClpV1-independent. |
| GO:0005576 extracellular region | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Combined IEA (ARBA plus the UniProt "Secreted" subcellular location). Reason: Same claim as the EXP row, which shows it directly. Supporting Evidence: PMID:20114026 These data show that the H1-T6SS exports at least two VgrG-family proteins. |
| GO:0033103 protein secretion by the type VI secretion system | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002088178 (a VgrG clade, 13 leaf IBAs in P. aeruginosa, Yersinia pestis and Salmonella), seeded by VgrG1a, VgrG1b and VgrG1c. Reason: Core process. The IDA and IMP seeds on this protein are sound, so its appearance in WITH/FROM reflects experimental grounding on the target. The node term suits a clade of T6SS spike proteins. Supporting Evidence: PMID:21325275 In conclusion, VgrG1a and VgrG1c are essential for efficient Hcp1 secretion but can function independently. |
| GO:0033103 protein secretion by the type VI secretion system | IDA PMID:20114026 A type VI secretion system of Pseudomonas aeruginosa targets... | ACCEPT | Summary: Hood et al. 2010: PA2685 (then vgrG4) is among the most abundant proteins of the on-state H1-T6SS secretome, and the PA0091 PA2685 double deletion abolishes Hcp1 secretion. Reason: Sound seed; the protein is both exported by the system and required for Hcp1 export. Supporting Evidence: PMID:20114026 Western blot analysis revealed that Hcp1 secretion was abolished in both the ΞclpV1 and ΞvgrG1 ΞvgrG4 strains, however it was unaffected by tse deletion |
| GO:0033103 protein secretion by the type VI secretion system | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA prediction of the same process. Reason: Same claim as the experimental rows. Supporting Evidence: PMID:21325275 In conclusion, VgrG1a and VgrG1c are essential for efficient Hcp1 secretion but can function independently. |
| GO:0033103 protein secretion by the type VI secretion system | IMP PMID:21325275 Type VI secretion system in Pseudomonas aeruginosa: secretio... | ACCEPT | Summary: Hachani et al. 2011: the single vgrG1c deletion leaves residual secretion; combined with vgrG1a deletion, Hcp1 secretion is abolished. Reason: Sound seed (full text read). VgrG1c and VgrG1a are redundant for Hcp1 export, and VgrG proteins are needed for export of other substrates. Supporting Evidence: PMID:21325275 However, when the vgrG1a mutation was combined with the vgrG1c mutation, Hcp1 secretion was abolished PMID:21325275 Our results demonstrate that VgrG proteins are not only secreted components but are essential for secretion of other T6SS substrates. |
| GO:0033104 type VI protein secretion system complex | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002088178, seeded by VgrG1a, VgrG1b and VgrG1c. Reason: Core complex. VgrG1c multimerises like a tail spike and is part of the H1-T6SS; the node term suits a VgrG clade. Supporting Evidence: PMID:21325275 We show that VgrG1a and VgrG1c form multimers, which confirmed the VgrG model predicting trimers similar to the tail spike. |
| GO:0033104 type VI protein secretion system complex | IDA PMID:20114026 A type VI secretion system of Pseudomonas aeruginosa targets... | ACCEPT | Summary: Hood et al. 2010: VgrGs, unlike the Tse cargo proteins, are required for Hcp1 export, so they behave as apparatus components. Reason: Sound seed for apparatus membership. Supporting Evidence: PMID:20114026 In a systematic analysis, Hcp secretion was shown to require all predicted core T6SS components, including VgrG-family proteins |
| GO:0033104 type VI protein secretion system complex | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA prediction of complex membership. Reason: Same claim as the experimental evidence. Supporting Evidence: PMID:21325275 We show that VgrG1a and VgrG1c form multimers, which confirmed the VgrG model predicting trimers similar to the tail spike. |
| GO:0033104 type VI protein secretion system complex | IMP PMID:21325275 Type VI secretion system in Pseudomonas aeruginosa: secretio... | ACCEPT | Summary: Hachani et al. 2011: VgrG1c multimerises and is redundantly required with VgrG1a for Hcp1 secretion. Reason: Sound seed for apparatus membership. Supporting Evidence: PMID:21325275 In conclusion, VgrG1a and VgrG1c are essential for efficient Hcp1 secretion but can function independently. |
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Experiment: Image fluorescently tagged VgrG1a and VgrG1c alongside a tagged sheath in single cells, and score whether firing events contain one spike protein or both.
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