FliI is the ATP-hydrolyzing subunit of the cytoplasmic flagellar type III export apparatus. FliH and FliJ organize its assembly and coupling to the membrane export gate. In Pseudomonas putida KT2440 these functions are inferred from its conserved flagellar export-family identity. The membrane gate normally uses proton motive force; the cytoplasmic ATPase machinery improves export efficiency, and bypass conditions can support export without FliHI. ATP-driven export without bulk proton motive force has also been reconstituted in Salmonella membrane vesicles.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: FliI binds ATP as its catalytic substrate. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. ATP binding is a genuine central substrate interaction; it is not an ontology ancestor of ATPase catalysis and is not made peripheral by the existence of a catalytic term. Supporting Evidence: PMID:8943245 It had an ATPase activity of 0.16 s-1 at 25 degrees C and pH 7, and a Km for ATP of 0.3 mM; Mg2+ was required. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: fliI has a soluble cytoplasmic pool participating in export-complex assembly. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. The soluble carrier/ATPase pool is distinct from its transient association with the membrane-bound export apparatus. Supporting Evidence: PMID:21934659 The export apparatus consists of three soluble proteins, FliH, FliI and FliJ, and six integral membrane proteins, FlhA, FlhB, FliO, FliP, FliQ and FliR file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0008564 protein-exporting ATPase activity | IEA GO_REF:0000003 | ACCEPT | Summary: FliI couples ATP hydrolysis to export-machine activity. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. Purified homolog ATPase kinetics and reconstitution with FliH/FliJ support this activity. PMF normally drives the gate, but Salmonella ΞFoF1 inverted membrane vesicles with FliHI, FliJ and MgATP also exported proteins without bulk PMF; this term does not imply that isolated FliI forms the transmembrane channel. Supporting Evidence: PMID:8943245 It had an ATPase activity of 0.16 s-1 at 25 degrees C and pH 7, and a Km for ATP of 0.3 mM; Mg2+ was required. PMID:29946050 Therefore, we conclude that flagellar protein export can be driven by ATP hydrolysis by FliI in the absence of bulk PMF. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0015986 proton motive force-driven ATP synthesis | IEA GO_REF:0000108 | REMOVE | Summary: FliI is an export ATPase, not the catalytic subunit of a proton-coupled ATP synthase. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. The specialized FliI signatures separate this protein from its F1-beta relatives. In the reconstitution, endogenous FoF1 ATP synthase was genetically removed while FliI-supported export remained; ATP synthase and FliI are distinct molecular systems. This is paralog/function over-transfer, not inferred loss from lack of an assay. Supporting Evidence: PMID:29946050 Therefore, we conclude that flagellar protein export can be driven by ATP hydrolysis by FliI in the absence of bulk PMF. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0016887 ATP hydrolysis activity | IEA GO_REF:0000002 | ACCEPT | Summary: FliI catalyzes ATP hydrolysis. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. GO:0008564 is not currently an is_a/part_of descendant of GO:0016887: one is classified as a translocase and the other as the hydrolysis reaction. Retain the independently supported hydrolysis claim rather than impose a false refinement. Supporting Evidence: PMID:8943245 It had an ATPase activity of 0.16 s-1 at 25 degrees C and pH 7, and a Km for ATP of 0.3 mM; Mg2+ was required. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0030254 protein secretion by the type III secretion system | IEA GO_REF:0000002 | ACCEPT | Summary: FliI performs catalytic work in the flagellar type III export machinery. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. ATP hydrolysis and substrate delivery/gate activation are direct steps in secretion; the assignment is not based only on a motility phenotype. Supporting Evidence: PMID:29946050 Therefore, we conclude that flagellar protein export can be driven by ATP hydrolysis by FliI in the absence of bulk PMF. PMID:29946050 These results show that the FliH2/FliI complex externally added in solution can assemble onto the export gate complex to form a functional export apparatus. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0030257 type III protein secretion system complex | IEA GO_REF:0000002 | ACCEPT | Summary: FliI is the ATPase subunit of a type III secretion apparatus. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. The flagellar export machinery is a type III system. GO:0120102 is not an is_a/part_of descendant of GO:0030257, so anatomical specificity alone does not justify hierarchy refinement. Supporting Evidence: PMID:29946050 The flagellar protein export apparatus consists of the transmembrane gate complex formed by FlhA, FlhB, FliP, FliQ, and FliR and the cytoplasmic ATPase complex composed of FliH, FliI, and FliJ file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0044780 bacterial-type flagellum assembly | IEA GO_REF:0000002 | ACCEPT | Summary: fliI performs a component step of flagellar construction. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. FliI is the ATP-hydrolyzing subunit of the cytoplasmic flagellar type III export apparatus. FliH and FliJ organize its assembly and coupling to the membrane export gate. This is direct machinery participation: it exports or guides structural substrates, rather than merely being required in a knockout experiment. Supporting Evidence: PMID:8943245 It had an ATPase activity of 0.16 s-1 at 25 degrees C and pH 7, and a Km for ATP of 0.3 mM; Mg2+ was required. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0046933 proton-transporting ATP synthase activity, rotational mechanism | IEA GO_REF:0000118 | REMOVE | Summary: FliI is an export ATPase, not the catalytic subunit of a proton-coupled ATP synthase. Reason: The KT2440 assignment is inferred from the target-specific NCBIfam/InterPro classification and conserved export-system context; the mechanistic experiments cited here used Salmonella, not KT2440. The specialized FliI signatures separate this protein from its F1-beta relatives. In the reconstitution, endogenous FoF1 ATP synthase was genetically removed while FliI-supported export remained; ATP synthase and FliI are distinct molecular systems. This is paralog/function over-transfer, not inferred loss from lack of an assay. Supporting Evidence: PMID:29946050 Therefore, we conclude that flagellar protein export can be driven by ATP hydrolysis by FliI in the absence of bulk PMF. file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
| GO:0071973 bacterial-type flagellum-dependent cell motility | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: fliI supports the function of the motility organelle through export of its structural components. Reason: Retain the existing broad functional participation claim, while identifying export/assembly as the direct core work. Same-role E. coli and Salmonella FliH/FliJ proteins consistently carry this term, including E. coli NAS annotations from PMID31337100. Current GO:0071973 describes flagellum-driven locomotion; it is not restricted to ATPase torque-generating subunits. The independent primary mechanism establishes export and bypass-mutant studies connect this machinery to motility, but do not establish a direct torque-generating activity. This acceptance does not create a new motility assertion or equate phenotype with the catalytic mechanism. Supporting Evidence: PMID:18216858 A fliH fliI double null mutant was weakly motile. PMID:29946050 The flagellar protein export apparatus consists of the transmembrane gate complex formed by FlhA, FlhB, FliP, FliQ, and FliR and the cytoplasmic ATPase complex composed of FliH, FliI, and FliJ file:PSEPK/fliI/fliI-uniprot.txt DR NCBIfam; TIGR03496; FliI_clade1; 1. |
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