PilT (PA0395) is the retraction ATPase of the type IVa pilus of Pseudomonas aeruginosa, a member of the secretion NTPase (GspE/PilT) superfamily with conserved Walker A, Walker B, Asp Box and His Box motifs. It forms a cytoplasmic homohexamer that docks at the base of the pilus machine, opposite the extension ATPase PilB, and couples ATP hydrolysis to domain motions that depolymerise the pilus into pilin monomers returned to the inner membrane. PilT localises to both cell poles and also promotes retraction by its paralogue PilU. pilT mutants are hyperpiliated but cannot retract their pili, so they do not twitch and are resistant to pilus-specific phages, and they are attenuated in dissemination during infection.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO mapping from IPR006321 (PilT/PilU). Reason: Correct; PilT was crystallised with the ATP analogue AMP-PCP and hydrolyses ATP. ATP binding is implied by, and less informative than, the ATP hydrolysis activity rows, but is a valid separate claim of the nucleotide-bound structure. Supporting Evidence: PMID:20595000 Crystal structures of Pseudomonas aeruginosa PilT with and without bound beta,gamma-methyleneadenosine-5'-triphosphate have been solved |
| GO:0005737 cytoplasm | EXP PMID:15659660 Disparate subcellular localization patterns of Pseudomonas a... | ACCEPT | Summary: UniProt EXP from Chiang et al. 2005: functional YFP-PilT fusions are cytoplasmic and localise to both poles. Reason: Direct localisation of a complementing fluorescent fusion in P. aeruginosa; PilT is a soluble hexamer acting at the cytoplasmic face of the pilus machine. Supporting Evidence: PMID:15659660 PilB and PilT fusions localized to both poles, while PilU fusions localized only to the piliated pole. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping to cytoplasm. Reason: Same claim as the EXP row, which is experimentally supported. Supporting Evidence: file:PSEAE/pilT/pilT-uniprot.txt Cytoplasm {ECO:0000269|PubMed:15659660}. |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002020799, seeded by E. coli YggR (P52052), not by a PseudoCAP row. Reason: PilT has no transmembrane segment and is a soluble cytoplasmic hexamer (EXP cytoplasm, PMID:15659660), so cytosol is consistent with the direct data for this gene and with the soluble PilT-like ATPases of the node. Supporting Evidence: PMID:15659660 PilB and PilT fusions localized to both poles, while PilU fusions localized only to the piliated pole. |
| GO:0016887 ATP hydrolysis activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002020799, sole seed the PseudoCAP IDA on this protein (PMID:18174131); PilT in its own WITH/FROM is expected for a seed. Reason: Core activity. The node's eight leaves (PilT of Xanthomonas, Shewanella and Vibrio, YggR of E. coli and Salmonella, Yersinia YPO0940 and Coxiella DotB) are secretion NTPases sharing the catalytic Walker and Asp/His Box motifs, so ATP hydrolysis is an appropriately broad inherited claim. Supporting Evidence: PMID:18174131 Assay of purified 6xHis-tagged PilB, PilT and PilU from P. aeruginosa showed that all three proteins have ATPase activities in vitro. |
| GO:0016887 ATP hydrolysis activity | IDA PMID:18174131 Functional role of conserved residues in the characteristic ... | ACCEPT | Summary: PseudoCAP IDA from Chiang et al. 2008: purified His-tagged PilT hydrolyses ATP in vitro, and Asp Box and His Box mutations abolish the activity. Reason: Direct biochemical assay on the purified protein, with catalytic-residue mutants; this is the correct ATPase paper for PilB/PilT/PilU. Sole seed of the PTN002020799 ATP hydrolysis IBD. Supporting Evidence: PMID:18174131 Assay of purified 6xHis-tagged PilB, PilT and PilU from P. aeruginosa showed that all three proteins have ATPase activities in vitro. PMID:18174131 the third acidic residue in the Asp Box and the second His of the His Box were crucial for function; mutation of these residues caused loss of PilT ATPase activity in vitro |
| GO:0043107 type IV pilus-dependent motility | TAS PMID:20595000 P. aeruginosa PilT structures with and without nucleotide re... | ACCEPT | Summary: PseudoCAP TAS from the PilT structure paper (Misic et al. 2010). Reason: PilT powers the retraction step of the extension-retraction cycle that is twitching; pilT mutants are piliated but do not twitch, so PilT does the work of the process. Supporting Evidence: PMID:20595000 Type IV pili are bacterial extracellular filaments that can be retracted to create force and motility. Retraction is accomplished by the motor protein PilT. file:PSEAE/pilT/pilT-uniprot.txt Mutants retain surface pili but have lost twitching motility |
| GO:0043108 pilus retraction | TAS PMID:20595000 P. aeruginosa PilT structures with and without nucleotide re... | ACCEPT | Summary: PseudoCAP TAS from the PilT structure paper. Reason: Core process: PilT is the retraction motor. No type IV-specific child of GO:0043108 exists, so this is as precise as GO allows. Supporting Evidence: PMID:20595000 Retraction is accomplished by the motor protein PilT. PMID:18174131 PilB and PilT are bipolar proteins belonging to the secretion NTPase superfamily, and power pilus extension and retraction, respectively |
| GO:0044096 type IV pilus | TAS PMID:20595000 P. aeruginosa PilT structures with and without nucleotide re... | REMOVE | Summary: PseudoCAP TAS located_in type IV pilus from the PilT structure paper. Reason: GO:0044096 is the extracellular pilus fibre built of pilins. PilT is a soluble cytoplasmic hexameric ATPase (EXP cytoplasm, PMID:15659660) that acts at the base of the pilus machine; it is not a component of the fibre. The row conflates the assembly/retraction machine with the pilus itself. Not an IBD seed. Supporting Evidence: PMID:15659660 PilB and PilT fusions localized to both poles, while PilU fusions localized only to the piliated pole. PMID:20595000 Type IV pili are bacterial extracellular filaments that can be retracted to create force and motility. |
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Download this section (compressed HTML)Q: GO lacks a type IV pilus retraction term and a cellular component for the pilus machine distinct from the fibre (GO:0044096). Should these be added, so that motor and alignment proteins stop being annotated to the fibre?
Experiment: Measure ATPase activity of PilT in the presence of PilU, PilC and PilM to test whether partner binding stimulates hydrolysis, and relate this to retraction force and speed in vivo for the corresponding mutants.
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