Bacterial flagellar assembly and type III export

Gammaproteobacterial flagellar assembly and export mechanisms connecting the MS/C-ring platform, protein export, rod/hook construction and length control, late transcription, and filament completion. Pseudomonas putida, Escherichia coli and Salmonella exemplars ground the assembly/export roles; P. putida MotAB/MotCD and Vibrio alginolyticus PomAB resolve conditional motor function and coupling-ion differences.

MODULE:bacterial_flagellar_assembly_exportCOMPLETECONCRETEBiological Processmodules/bacterial_flagellar_assembly_export.yaml
bacterial-type flagellum assemblyGO:0044780
GO:0044780
bacterial-type flagellum assembly
Grounds ordered construction of the bacterial flagellum.
KEGG:ppu02040
Pseudomonas putida KT2440 flagellar assembly
Identifies the PSEPK regulatory, export, structural, and motor realization.
file:genes/ECOLI/fliI/fliI-ai-review.yaml
ECOLI fliI gene review
The completed E. coli fliI review grounds the flagellar export ATPase role at the type III export apparatus.
file:projects/P_PUTIDA/deep-research/PSEPK__bacterial_flagellar_assembly_export__ppu02040-deep-research-openscientist.md
OpenScientist PSEPK flagellar assembly pathway review
The species-aware report finds all six architectural parts represented, identifies omitted export, switch, rod, and junction subunits, and flags KEGG name-collision and regulatory-boundary issues.

The conserved assembly/export architecture is represented within Gammaproteobacteria, with experimentally studied Pseudomonas, enterobacterial and Vibrio realizations. This is not a claim that all members of the taxon possess flagella or this regulatory/stator configuration. The selected components do not establish de novo whole-flagellum sufficiency: FliE, compatible envelope/LP-ring assembly, substrate supply, chaperones, membrane insertion and energy conditions remain explicit external prerequisites. Gram-positive absence of the LP ring and outgroup motor structures limit extrapolation rather than expand the declared taxon automatically. Chemotactic sensing is handled by its separate module; the switch is the motor output. Assembly/export, normal export efficiency, torque production and condition-specific swimming are distinct endpoints. The FliA/FlgM regulatory part is conditional on the source of late proteins, and FlgM is optional as a negative regulator. Stator pairs are optional for assembly and required for powered rotation. The official FliI PANTHER label contains ATP SYNTHASE but does not imply that reaction. FlgD retains a named family descriptor with exact members because available verified identifiers describe domains or an N-terminal region, not a justified whole-protein family. No PANTHER ID or ancestral placement is guessed.

11Nodes
7Parts
1Variant Sets
3Variants
31Annotons
7Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:bacterial_flagellar_assembly_export deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Reaction chaining (advisory)

✓ every PRECEDES step chains, or its break is acknowledged via chaining_status.

  • ms_ring_switch_assembly → flagellar_type_iii_export [NOT_CHECKED]
  • rod_hook_assembly → filament_completion [NOT_CHECKED]
  • ms_ring_switch_assembly → motab_stator_installation [NOT_CHECKED]

Function consistency and core coverage

No functional claims were checked. This does not establish consistency with gene or family reviews.

Feedback loops (advisory, prose-driven: a regulator counts as "feedback" when its own description says so)

✓ every negative regulator described as feedback has an upstream edge closing the loop.

  • flgm_antisigma_factor ⊣ flia_sigma_factor [input]
    flgm_antisigma_factor is a negative regulator with no upstream edge (not described as feedback)

Gene-review completeness (38/38 grounded genes reviewed)

38 complete review(s) · 18 with deep research · 0 missing review · 20 reviewed but lacking deep research

Gene Review Complete Deep research
flgB Q88ER2 ✓ ✓ ✗
flgC Q88ER3 ✓ ✓ ✗
flgD Q88ER4 ✓ ✓ ✗
flgE P0A1J1 ✓ ✓ ✗
flgE Q88ER5 ✓ ✓ ✓
flgF Q88ER7 ✓ ✓ ✗
flgG Q88ER8 ✓ ✓ ✓
flgK Q88ES2 ✓ ✓ ✓
flgL Q88ES3 ✓ ✓ ✓
flgM P26477 ✓ ✓ ✗
flgM Q88EQ8 ✓ ✓ ✓
flhA P40729 ✓ ✓ ✗
flhA Q88EV8 ✓ ✓ ✓
flhB Q88EV1 ✓ ✓ ✗
fliA Q88EW1 ✓ ✓ ✓
fliC Q88ES5 ✓ ✓ ✓
fliD Q88ES7 ✓ ✓ ✓
fliF Q88ET4 ✓ ✓ ✓
fliG Q88ET5 ✓ ✓ ✓
fliH Q88ET6 ✓ ✓ ✗
fliI P26465 ✓ ✓ ✓
fliI P52612 ✓ ✓ ✓
fliI Q88ET7 ✓ ✓ ✓
fliJ P0A1K1 ✓ ✓ ✗
fliJ Q88ET8 ✓ ✓ ✗
fliK P26416 ✓ ✓ ✗
fliK Q88EU2 ✓ ✓ ✓
fliM Q88EU5 ✓ ✓ ✗
fliN Q88EU6 ✓ ✓ ✗
fliP Q88EU8 ✓ ✓ ✓
fliQ Q88EU9 ✓ ✓ ✗
fliR Q88EV0 ✓ ✓ ✗
motA Q88DC2 ✓ ✓ ✓
motB Q88DC3 ✓ ✓ ✓
pomA O06873 ✓ ✓ ✗
pomB O06874 ✓ ✓ ✗
PP_4335 Q88EW7 ✓ ✓ ✗
PP_4336 Q88EW6 ✓ ✓ ✗

Details

Context
GammaproteobacteriaNCBITaxon:1236
Bacterial flagellar assembly and exportBiological Processbacterial_flagellar_assembly_export
bacterial-type flagellum assemblyGO:0044780
Context
GammaproteobacteriaNCBITaxon:1236

Connections

rod_hook_assembly -> flia_sigma_factor Positively Regulates
flia_sigma_factor -> filament_completion Positively Regulates
Part 4: late flagellar transcription control (optional)

Regulatory context for native late-protein supply. This part can be omitted only when substrate expression is supplied externally or its regulation is outside the assembly endpoint; omission does not establish FliA-independent native transcription.

FliA and FlgM transcriptional checkpointRegulatory Stepflagellar_late_transcription
PMID:34859548
Transcriptional organization and regulation of the Pseudomonas putida flagellar system.
P. putida expression analyses support a FleQ/sigma54-led hierarchy with FliA-dependent late outputs; Salmonella FlhDC regulation is not substituted for this hierarchy.
PMID:10972838
Completion of the hook-basal body complex of the Salmonella typhimurium flagellum is coupled to FlgM secretion and fliC transcription.
In induced Salmonella flagellar assembly, late fliC expression coincides with FlgM secretion and completion of the hook-basal body; target-specific timing is not transferred to PSEPK.

FlgM deletion removes the brake. Requiring both FliA and FlgM as positive Boolean inputs would invert the biology.

Annotons

FliA sigma factor
flia_sigma_factor
Participant: Family: flagellar sigma factor FliA family
Family:
flagellar sigma factor FliA familyPANTHER:PTHR30385:SF7
Representative Members: fliA (PSEPK)UniProtKB:Q88EW1

Directs late flagellar gene transcription after assembly reaches the secretion checkpoint.

PMID:34859548
Transcriptional organization and regulation of the Pseudomonas putida flagellar system.
The native P. putida expression hierarchy places FliA on late filament, stator and chemotaxis outputs.
FliA activation of Class III genes enables synthesis of the filament, one stator complex and completion of the chemotaxis apparatus.

Connections

flgm_antisigma_factor -> flia_sigma_factor Negatively Regulates
Part: negative checkpoint regulator (optional)
FlgM inhibition relieved by exportRegulatory Stepflgm_checkpoint_brake

Annotons

FlgM anti-sigma factor
flgm_antisigma_factor
Participant: Family: flagellar anti-sigma factor FlgM family
Family:
flagellar anti-sigma factor FlgM familyInterPro:IPR007412
Representative Members: flgM (PSEPK)UniProtKB:Q88EQ8 flgM (SALTY)UniProtKB:P26477

Restrains FliA until the hook-basal-body export checkpoint is satisfied.

PMID:10972838
Completion of the hook-basal body complex of the Salmonella typhimurium flagellum is coupled to FlgM secretion and fliC transcription.
FlgM inhibits sigma28 until secretion relieves repression at hook-basal-body completion.
Both FlgM secretion and class 3 gene expression occur upon completion of the hook-basal body structure.
Part 2: flagellar type III export
Membrane export gate and cytosolic ATPaseProtein Complexflagellar_type_iii_export
PMID:21934659
An energy transduction mechanism used in bacterial flagellar type III protein export.
FliH/FliI assist FliJ engagement with FlhA, activating efficient membrane-potential-driven export.
a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH-FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus.
PMID:29946050
In Vitro Reconstitution of Functional Type III Protein Export and Insights into Flagellar Assembly.
FliI hydrolysis can drive export without bulk proton motive force in the defined membrane-vesicle assay.
ATP hydrolysis by FliI can drive the protein export without PMF.
PMID:18216858
Distinct roles of the FliI ATPase and proton motive force in bacterial flagellar protein export.
A Salmonella fliH fliI double-null mutant retains weak motility, with export improved by gate suppressors; absence of these accessory proteins does not establish universal impossibility of export.
A fliH fliI double null mutant was weakly motile.
PMID:26943926
The Bacterial Flagellar Type III Export Gate Complex Is a Dual Fuel Engine That Can Use Both H+ and Na+ for Flagellar Protein Export.
FlhA can conduct H+ and Na+, but conditional sodium-supported export in bypass backgrounds is separate from sodium-driven stator torque.
In wild-type cells, however, neither Na+ nor phenamil affected protein export
PMID:40833400
A β-cap on the FliPQR protein-export channel acts as the cap for initial flagellar rod assembly.
The FliPQR protein-conducting channel also templates initial rod assembly.
Thus, the FliPQR complex also acts as a template for rod assembly.
PMID:29967543
Structure of the core of the type III secretion system export apparatus.
FliP, FliQ and FliR form a specialized polypeptide channel with noncanonical topology.
The complex is a P5Q4R1 assembly consistent with the dominant species in our earlier nMS data of the flagellar system

The represented configuration includes FliH/FliI-assisted export. Bypass mutants and reconstituted ATP-only export are explicit experimental exceptions, not evidence that all normal cells dispense with ATPase assistance or ion gradients.

Annotons

FlhA export-gate component
flha_export_gate
Participant: Family: FlhA family
Family:
FlhA familyPANTHER:PTHR30161:SF1
Representative Members: flhA (PSEPK)UniProtKB:Q88EV8 flhA (SALTY)UniProtKB:P40729

Provides the export platform and ion-coupled gate activity; ion requirements depend on the FliH/FliI/FliJ and genetic context.

PMID:21934659
An energy transduction mechanism used in bacterial flagellar type III protein export.
FliH/FliI assist FliJ engagement with FlhA, activating efficient membrane-potential-driven export.
a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH-FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus.
PMID:26943926
The Bacterial Flagellar Type III Export Gate Complex Is a Dual Fuel Engine That Can Use Both H+ and Na+ for Flagellar Protein Export.
FlhA can conduct H+ and Na+, but conditional sodium-supported export in bypass backgrounds is separate from sodium-driven stator torque.
In wild-type cells, however, neither Na+ nor phenamil affected protein export
FliP export-gate component
flip_export_gate
Participant: Family: FliP family
Family:
FliP familyPANTHER:PTHR30587:SF0
Representative Members: fliP (PSEPK)UniProtKB:Q88EU8

Conserved membrane export-gate component.

PMID:40833400
A β-cap on the FliPQR protein-export channel acts as the cap for initial flagellar rod assembly.
The FliPQR protein-conducting channel also templates initial rod assembly.
Thus, the FliPQR complex also acts as a template for rod assembly.
FlhB export-switch component
flhb_export_switch
Participant: Family: FlhB family
Family:
FlhB familyPANTHER:PTHR30531:SF12
Representative Members: flhB (PSEPK)UniProtKB:Q88EV1

Participates in export-substrate specificity switching.

PMID:19732341
Interaction of FliK with the bacterial flagellar hook is required for efficient export specificity switching.
FliK interacts with FlhB to switch export specificity at hook completion.
FliK-FlhB interaction switches export specificity of the bacterial flagellar protein export apparatus to stop hook protein export at an appropriate timing for hook length control.
FliQ export-gate component
fliq_export_gate
Participant: Family: FliQ family
Family:
FliQ familyPANTHER:PTHR34040:SF8
Representative Members: fliQ (PSEPK)UniProtKB:Q88EU9

Forms part of the membrane export-gate core.

PMID:40833400
A β-cap on the FliPQR protein-export channel acts as the cap for initial flagellar rod assembly.
The FliPQR protein-conducting channel also templates initial rod assembly.
Thus, the FliPQR complex also acts as a template for rod assembly.
PMID:29967543
Structure of the core of the type III secretion system export apparatus.
FliP, FliQ and FliR form a specialized polypeptide channel with noncanonical topology.
The complex is a P5Q4R1 assembly consistent with the dominant species in our earlier nMS data of the flagellar system
FliR export-gate component
flir_export_gate
Participant: Family: FliR family
Family:
FliR familyPANTHER:PTHR30065:SF8
Representative Members: fliR (PSEPK)UniProtKB:Q88EV0

Forms part of the membrane export-gate core.

PMID:40833400
A β-cap on the FliPQR protein-export channel acts as the cap for initial flagellar rod assembly.
The FliPQR protein-conducting channel also templates initial rod assembly.
Thus, the FliPQR complex also acts as a template for rod assembly.
FliI export ATPase
flii_export_atpase
Participant: Family: FliI flagellar export ATPase family
Family:
FliI flagellar export ATPase familyPANTHER:PTHR15184:SF81
Representative Members: fliI (PSEPK)UniProtKB:Q88ET7 fliI (ECOLI)UniProtKB:P52612 fliI (SALTY)UniProtKB:P26465

Hydrolyzes ATP in the assisted export machinery; the official family name does not establish ATP synthesis, and bypass/reconstitution conditions qualify universal energy claims.

PMID:29946050
In Vitro Reconstitution of Functional Type III Protein Export and Insights into Flagellar Assembly.
FliI hydrolysis can drive export without bulk proton motive force in the defined membrane-vesicle assay.
ATP hydrolysis by FliI can drive the protein export without PMF.
PMID:21934659
An energy transduction mechanism used in bacterial flagellar type III protein export.
FliH/FliI assist FliJ engagement with FlhA, activating efficient membrane-potential-driven export.
a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH-FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus.
FliH export ATPase regulator
flih_atpase_regulator
Participant: Family: FliH family
Family:
FliH familyPANTHER:PTHR34982:SF1
Representative Members: fliH (PSEPK)UniProtKB:Q88ET6

Regulates and positions the FliI ATPase at the export apparatus.

PMID:21934659
An energy transduction mechanism used in bacterial flagellar type III protein export.
FliH/FliI assist FliJ engagement with FlhA, activating efficient membrane-potential-driven export.
a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH-FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus.
FliJ central stalk and export-gate activator
flij_export_chaperone
Participant: Family: FliJ family
Family:
FliJ familyPANTHER:PTHR38786:SF1
Representative Members: fliJ (PSEPK)UniProtKB:Q88ET8 fliJ (SALTY)UniProtKB:P0A1K1

Activates FlhA-dependent export with FliH/FliI assistance and promotes FliI ring assembly; this is not independently enabled motor torque or a generic holdase claim.

PMID:21934659
An energy transduction mechanism used in bacterial flagellar type III protein export.
FliH/FliI assist FliJ engagement with FlhA, activating efficient membrane-potential-driven export.
a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH-FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus.
Part 1: basal-body MS ring and switch assembly
FliF MS ring and FliG switchProtein Complexms_ring_switch_assembly
PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
Structural review places FliF, FliG/FliM/FliN, rod and hook proteins, junction proteins, flagellin and FliD in distinct assembly structures. Salmonella stoichiometry is not a measurement on the PSEPK exemplars.
PMID:25613993
The bacterial flagellar motor and its structural diversity.
The review distinguishes a conserved MS-ring/C-ring/rod/export core from species-dependent accessory structures and sodium- versus proton-driven motors.

Annotons

FliF MS-ring component
flif_ms_ring
Participant: Family: FliF family
Family:
FliF familyPANTHER:PTHR30046:SF0
Representative Members: fliF (PSEPK)UniProtKB:Q88ET4

Forms the membrane-embedded MS ring that anchors export and switch components.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
The structural review assigns MS-ring, C-ring, axial junction, filament and cap roles; detailed Salmonella stoichiometry is not transferred to KT2440.
The Salmonella flagellum consists of several ring structures called the MS-ring (FliF), the C-ring (FliG, FliM, FliN), the P-ring (FlgI), and the L-ring (FlgH), and an axial structure.
FliG switch component
flig_switch
Participant: Family: FliG family
Family:
FliG familyPANTHER:PTHR30534
Representative Members: fliG (PSEPK)UniProtKB:Q88ET5

Couples the rotor to stator torque and chemotactic switching.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
The structural review assigns MS-ring, C-ring, axial junction, filament and cap roles; detailed Salmonella stoichiometry is not transferred to KT2440.
The Salmonella flagellum consists of several ring structures called the MS-ring (FliF), the C-ring (FliG, FliM, FliN), the P-ring (FlgI), and the L-ring (FlgH), and an axial structure.
FliM switch component
flim_switch
Participant: Family: FliM family
Family:
FliM familyPANTHER:PTHR30034:SF3
Representative Members: fliM (PSEPK)UniProtKB:Q88EU5

Forms the C-ring switch and receives chemotactic switching inputs.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
The structural review assigns MS-ring, C-ring, axial junction, filament and cap roles; detailed Salmonella stoichiometry is not transferred to KT2440.
The Salmonella flagellum consists of several ring structures called the MS-ring (FliF), the C-ring (FliG, FliM, FliN), the P-ring (FlgI), and the L-ring (FlgH), and an axial structure.
FliN switch component
flin_switch
Participant: Family: FliN family
Family:
FliN familyPANTHER:PTHR43484:SF1
Representative Members: fliN (PSEPK)UniProtKB:Q88EU6

Forms the C-ring switch and supports rotor assembly.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
The structural review assigns MS-ring, C-ring, axial junction, filament and cap roles; detailed Salmonella stoichiometry is not transferred to KT2440.
The Salmonella flagellum consists of several ring structures called the MS-ring (FliF), the C-ring (FliG, FliM, FliN), the P-ring (FlgI), and the L-ring (FlgH), and an axial structure.
Part 3: rod-hook construction and length control
Distal rod, hook, and hook-length checkpointBiological Processrod_hook_assembly
PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
Structural review places FliF, FliG/FliM/FliN, rod and hook proteins, junction proteins, flagellin and FliD in distinct assembly structures. Salmonella stoichiometry is not a measurement on the PSEPK exemplars.
PMID:40833400
A β-cap on the FliPQR protein-export channel acts as the cap for initial flagellar rod assembly.
The FliPQR channel also templates the initial rod structure; this connects export-gate assembly to axial construction.

Annotons

FlgG distal rod
flgg_distal_rod
Participant: Family: FlgG family
Family:
FlgG familyPANTHER:PTHR30435:SF19
Representative Members: flgG (PSEPK)UniProtKB:Q88ER8

Builds the distal rod through the periplasm.

PMID:33931760
Molecular structure of the intact bacterial flagellar basal body.
Salmonella basal-body structures identify FlgB/FlgC/FlgF in the proximal rod and FlgG in the distal rod; dedicated families support the corresponding KT2440 assignments.
The proximal rod is composed of four different proteins, FliE, FlgB, FlgC and FlgF, while the distal rod is composed of multiple copies of just one protein, FlgG
FlgB proximal rod
flgb_proximal_rod
Participant: Family: FlgB family
Family:
FlgB familyPANTHER:PTHR30435:SF12
Representative Members: flgB (PSEPK)UniProtKB:Q88ER2

Contributes to the proximal rod linking the MS ring to distal structures.

PMID:33931760
Molecular structure of the intact bacterial flagellar basal body.
Salmonella basal-body structures identify FlgB/FlgC/FlgF in the proximal rod and FlgG in the distal rod; dedicated families support the corresponding KT2440 assignments.
The proximal rod is composed of four different proteins, FliE, FlgB, FlgC and FlgF, while the distal rod is composed of multiple copies of just one protein, FlgG
FlgC proximal rod
flgc_proximal_rod
Participant: Family: FlgC family
Family:
FlgC familyPANTHER:PTHR30435:SF29
Representative Members: flgC (PSEPK)UniProtKB:Q88ER3

Contributes to the proximal rod linking the MS ring to distal structures.

PMID:33931760
Molecular structure of the intact bacterial flagellar basal body.
Salmonella basal-body structures identify FlgB/FlgC/FlgF in the proximal rod and FlgG in the distal rod; dedicated families support the corresponding KT2440 assignments.
The proximal rod is composed of four different proteins, FliE, FlgB, FlgC and FlgF, while the distal rod is composed of multiple copies of just one protein, FlgG
FlgF rod component
flgf_rod
Participant: Family: FlgF family
Family:
FlgF familyPANTHER:PTHR30435:SF18
Representative Members: flgF (PSEPK)UniProtKB:Q88ER7

Connects proximal and distal rod structures.

PMID:33931760
Molecular structure of the intact bacterial flagellar basal body.
Salmonella basal-body structures identify FlgB/FlgC/FlgF in the proximal rod and FlgG in the distal rod; dedicated families support the corresponding KT2440 assignments.
The proximal rod is composed of four different proteins, FliE, FlgB, FlgC and FlgF, while the distal rod is composed of multiple copies of just one protein, FlgG
FlgD hook assembly cap
flgd_hook_cap
Participant: Family: FlgD hook assembly family
Family:
FlgD hook assembly family
Representative Members: flgD (PSEPK)UniProtKB:Q88ER4

Acts as the hook assembly cap before filament-junction completion.

PMID:34785766
Structure of the bacterial flagellar hook cap provides insights into a hook assembly mechanism.
FlgD assembles the transient hook cap that scaffolds FlgE polymerization.
we report the crystal structure of the hook cap composed of five subunits of FlgD from Salmonella enterica at 3.3
FlgE hook
flge_hook
Participant: Family: FlgE hook family
Family:
FlgE hook familyPANTHER:PTHR30435:SF1
Representative Members: flgE (PSEPK)UniProtKB:Q88ER5 flgE (SALTY)UniProtKB:P0A1J1

Polymerizes the flexible hook joining rod and filament.

PMID:29946050
In Vitro Reconstitution of Functional Type III Protein Export and Insights into Flagellar Assembly.
Exported FlgE polymerizes into hooks when FlgD is supplied in the vesicle reconstruction.
In the presence of FlgD, the transported FlgE monomers assembled into the hook structure on the basal body
FliK hook-length control
flik_length_control
Participant: Family: FliK family
Family:
FliK familyPANTHER:PTHR37533:SF2
Representative Members: fliK (PSEPK)UniProtKB:Q88EU2 fliK (SALTY)UniProtKB:P26416

Triggers export-substrate switching when the hook reaches its target length.

PMID:19732341
Interaction of FliK with the bacterial flagellar hook is required for efficient export specificity switching.
FliK interacts with FlhB to switch export specificity at hook completion.
FliK-FlhB interaction switches export specificity of the bacterial flagellar protein export apparatus to stop hook protein export at an appropriate timing for hook length control.
Part 5: filament junction, polymerization, and capping
Hook-filament junction, flagellin filament, and capBiological Processfilament_completion
PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
Structural review places FliF, FliG/FliM/FliN, rod and hook proteins, junction proteins, flagellin and FliD in distinct assembly structures. Salmonella stoichiometry is not a measurement on the PSEPK exemplars.

Annotons

FlgK hook-filament junction
flgk_junction
Participant: Family: FlgK family
Family:
FlgK familyPANTHER:PTHR30033:SF1
Representative Members: flgK (PSEPK)UniProtKB:Q88ES2

Forms the proximal hook-filament junction.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
FlgK/FlgL join the hook to FliC and FliD caps the filament; FliE and additional envelope structures remain real prerequisites outside this represented component set.
The axial structure is divided into 5 parts: the rod (FliE, FlgB, FlgC, FlgF, FlgG), the hook (FlgE), the hook–filament junction (FlgK, FlgL), the filament (FliC or FljB) and the filament cap (FliD)
FliC flagellin
flic_flagellin
Participant: Family: bacterial flagellin family
Family:
bacterial flagellin familyPANTHER:PTHR42792:SF2
Representative Members: fliC (PSEPK)UniProtKB:Q88ES5

Polymerizes into the extracellular flagellar filament.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
FlgK/FlgL join the hook to FliC and FliD caps the filament; FliE and additional envelope structures remain real prerequisites outside this represented component set.
The axial structure is divided into 5 parts: the rod (FliE, FlgB, FlgC, FlgF, FlgG), the hook (FlgE), the hook–filament junction (FlgK, FlgL), the filament (FliC or FljB) and the filament cap (FliD)
FlgL hook-filament junction
flgl_junction
Participant: Family: FlgL family
Family:
FlgL familyPANTHER:PTHR42792:SF1
Representative Members: flgL (PSEPK)UniProtKB:Q88ES3

Forms the distal hook-filament junction with FlgK.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
FlgK/FlgL join the hook to FliC and FliD caps the filament; FliE and additional envelope structures remain real prerequisites outside this represented component set.
The axial structure is divided into 5 parts: the rod (FliE, FlgB, FlgC, FlgF, FlgG), the hook (FlgE), the hook–filament junction (FlgK, FlgL), the filament (FliC or FljB) and the filament cap (FliD)
FliD filament cap
flid_cap
Participant: Family: FliD cap family
Family:
FliD cap familyPANTHER:PTHR30288:SF0
Representative Members: fliD (PSEPK)UniProtKB:Q88ES7

Caps the distal filament and promotes flagellin incorporation.

PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
FlgK/FlgL join the hook to FliC and FliD caps the filament; FliE and additional envelope structures remain real prerequisites outside this represented component set.
The axial structure is divided into 5 parts: the rod (FliE, FlgB, FlgC, FlgF, FlgG), the hook (FlgE), the hook–filament junction (FlgK, FlgL), the filament (FliC or FljB) and the filament cap (FliD)
Part 6: conditional torque-generating stator installation (optional)

Optional for assembly/export, required as an appropriate complete branch for the motor-function endpoint. A motor with no active stator can be assembled without generating torque.

Matched ion-coupled stator pairsProtein Complexmotab_stator_installation
PMID:25613993
The bacterial flagellar motor and its structural diversity.
The review distinguishes a conserved MS-ring/C-ring/rod/export core from species-dependent accessory structures and sodium- versus proton-driven motors.
PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
In KT2440 FliC S267C assays, MotAB and MotCD differ by environment: MotAB loss strongly impairs liquid swimming, whereas MotCD loss slows semisolid-agar spreading.
Variant set: Compatible native stator pair by partner identity, motor background and coupling ion [Realizer] (One Or More)
PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
KT2440 MotAB and MotCD form matched alternative stators with different liquid and semisolid performance.
In homogeneous fluids, the MotAB stator is crucial to promote swimming motility, so the movement of ΔmotAB mutant cells in aqueous fluids is strongly impaired.
PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
MotCD contributes strongly to dispersal in structured media; its presence alone does not establish wild-type-like liquid swimming.
For both agar concentrations, the ΔmotAB culture spreads almost as quickly as the wild type, whereas the ΔmotCD culture spreads considerably more slowly.
PMID:18326582
Roles of charged residues in the C-terminal region of PomA, a stator component of the Na+-driven flagellar motor.
Matched PomA/PomB function is tested in native Vibrio ΔpomAB cells; separate E. coli hybrid experiments do not establish interchangeable native stator partners.
The mutant pomA gene was introduced along with pomB into the Δ pomAB strain NMB191
PMID:39766194
Structure and Dynamics of the Bacterial Flagellar Motor Complex.
Modern structures support five A and two B stator subunits rather than the legacy A4B2 definition; broad family membership does not determine coupling-ion selectivity.
Thus, 5 A:2 B is the common stoichiometry in the bacterial flagellar stator complex.

Each alternative requires both matched subunits. PSEPK MotAB and MotCD can coexist. A-family or B-family membership alone establishes neither pair compatibility nor coupling-ion specificity.

PSEPK MotAB statorProtein Complexmotab_native_pair
Context
Pseudomonas putida KT2440NCBITaxon:160488
PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
KT2440 MotAB and MotCD form matched alternative stators with different liquid and semisolid performance.
In homogeneous fluids, the MotAB stator is crucial to promote swimming motility, so the movement of ΔmotAB mutant cells in aqueous fluids is strongly impaired.

Especially important for homogeneous-fluid swimming. Channel mechanism is inferred from comparative stator studies.

Annotons

MotA stator subunit
mota_stator
Participant: Family: MotA family
Family:
MotA familyPANTHER:PTHR30433
Representative Members: motA (PSEPK)UniProtKB:Q88DC2

Membrane stator subunit contributing to proton-driven torque.

PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
KT2440 MotAB and MotCD form matched alternative stators with different liquid and semisolid performance.
In homogeneous fluids, the MotAB stator is crucial to promote swimming motility, so the movement of ΔmotAB mutant cells in aqueous fluids is strongly impaired.
MotB stator subunit
motb_stator
Participant: Family: MotB family
Family:
MotB familyPANTHER:PTHR30329
Representative Members: motB (PSEPK)UniProtKB:Q88DC3

Anchors the stator to peptidoglycan and contributes to proton-driven torque.

PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
KT2440 MotAB and MotCD form matched alternative stators with different liquid and semisolid performance.
In homogeneous fluids, the MotAB stator is crucial to promote swimming motility, so the movement of ΔmotAB mutant cells in aqueous fluids is strongly impaired.
PSEPK MOTCD statorProtein Complexmotcd_native_pair
Context
Pseudomonas putida KT2440NCBITaxon:160488
PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
MotCD contributes strongly to dispersal in structured media; its presence alone does not establish wild-type-like liquid swimming.
For both agar concentrations, the ΔmotAB culture spreads almost as quickly as the wild type, whereas the ΔmotCD culture spreads considerably more slowly.

proton coupling inferred; both reviewed partners and a compatible native motor/background are required.

Annotons

MotC stator subunit
motc_stator
Participant: Family: MotA-family A subunit in the MOTCD realization
Family:
MotA-family A subunit in the MOTCD realizationPANTHER:PTHR30433
Representative Members: PP_4336 (PSEPK)UniProtKB:Q88EW6

A-type subunit of the proton-driven MotCD flagellar stator: in the inner membrane it contributes to the stator proton channel that couples proton influx to torque on the rotor, supporting swimming of KT2440 through structured (semisolid) environments. Proton conductance and detailed channel architecture are inferred from homologous stators; native KT2440 motility is directly tested.

PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
MotCD contributes strongly to dispersal in structured media; its presence alone does not establish wild-type-like liquid swimming.
For both agar concentrations, the ΔmotAB culture spreads almost as quickly as the wild type, whereas the ΔmotCD culture spreads considerably more slowly.
MotD stator subunit
motd_stator
Participant: Family: MotB-family B subunit in the MOTCD realization
Family:
MotB-family B subunit in the MOTCD realizationPANTHER:PTHR30329
Representative Members: PP_4335 (PSEPK)UniProtKB:Q88EW7

B-type subunit of the proton-driven MotCD flagellar stator: its transmembrane helix contributes to the stator proton channel and its periplasmic OmpA-like domain is expected to anchor the stator to peptidoglycan, supporting KT2440 swimming through semisolid environments. Proton conductance and detailed channel architecture are inferred from homologous stators; native KT2440 motility is directly tested.

PMID:36409076
Role of the Two Flagellar Stators in Swimming Motility of Pseudomonas putida.
MotCD contributes strongly to dispersal in structured media; its presence alone does not establish wild-type-like liquid swimming.
For both agar concentrations, the ΔmotAB culture spreads almost as quickly as the wild type, whereas the ΔmotCD culture spreads considerably more slowly.
VIBAL POMAB statorProtein Complexpomab_native_pair
Context
Vibrio alginolyticusNCBITaxon:663
PMID:18326582
Roles of charged residues in the C-terminal region of PomA, a stator component of the Na+-driven flagellar motor.
Matched PomA/PomB function is tested in native Vibrio ΔpomAB cells; separate E. coli hybrid experiments do not establish interchangeable native stator partners.
The mutant pomA gene was introduced along with pomB into the Δ pomAB strain NMB191
PMID:39793043
Structural insight into sodium ion pathway in the bacterial flagellar stator from marine Vibrio.
Vibrio PomAB structures resolve the sodium pathway and phenamil-sensitive mechanism; sequence-matched constructs and native functional assays are distinguished from heterologous purification.
we determined the structures of the sodium-driven stator of Vibrio, namely PomAB, in the presence and absence of sodium ions

sodium coupling experimentally supported; both reviewed partners and a compatible native motor/background are required.

Annotons

PomA stator subunit
poma_stator
Participant: Family: MotA-family A subunit in the POMAB realization
Family:
MotA-family A subunit in the POMAB realizationPANTHER:PTHR30433
Representative Members: pomA (VIBAL)UniProtKB:O06873

Contributes the sodium-conducting and rotor-contacting A subunit to the PomAB torque-generating stator.

PMID:18326582
Roles of charged residues in the C-terminal region of PomA, a stator component of the Na+-driven flagellar motor.
Matched PomA/PomB function is tested in native Vibrio ΔpomAB cells; separate E. coli hybrid experiments do not establish interchangeable native stator partners.
The mutant pomA gene was introduced along with pomB into the Δ pomAB strain NMB191
PMID:39793043
Structural insight into sodium ion pathway in the bacterial flagellar stator from marine Vibrio.
Vibrio PomAB structures resolve the sodium pathway and phenamil-sensitive mechanism; sequence-matched constructs and native functional assays are distinguished from heterologous purification.
we determined the structures of the sodium-driven stator of Vibrio, namely PomAB, in the presence and absence of sodium ions
PomB stator subunit
pomb_stator
Participant: Family: MotB-family B subunit in the POMAB realization
Family:
MotB-family B subunit in the POMAB realizationPANTHER:PTHR30329
Representative Members: pomB (VIBAL)UniProtKB:O06874

Contributes the membrane ion-pathway B subunit and periplasmic anchoring/regulatory region to the PomAB sodium-driven stator.

PMID:18326582
Roles of charged residues in the C-terminal region of PomA, a stator component of the Na+-driven flagellar motor.
Matched PomA/PomB function is tested in native Vibrio ΔpomAB cells; separate E. coli hybrid experiments do not establish interchangeable native stator partners.
The mutant pomA gene was introduced along with pomB into the Δ pomAB strain NMB191
PMID:39793043
Structural insight into sodium ion pathway in the bacterial flagellar stator from marine Vibrio.
Vibrio PomAB structures resolve the sodium pathway and phenamil-sensitive mechanism; sequence-matched constructs and native functional assays are distinguished from heterologous purification.
we determined the structures of the sodium-driven stator of Vibrio, namely PomAB, in the presence and absence of sodium ions