Bacterial twin-arginine protein translocation

A species-neutral bacterial membrane-translocation module for export of folded proteins bearing an N-terminal twin-arginine signal peptide by the Tat machinery. TatC and TatB form the substrate receptor that binds the signal peptide and the folded precursor; TatA is then recruited in a proton-motive-force-dependent manner and oligomerizes to carry out passage across the cytoplasmic membrane without ATP. Signal-peptide recognition, receptor organization and translocation are modeled as separate roles.

MODULE:bacterial_twin_arginine_translocationCOMPLETECONCRETEBiological Processmodules/bacterial_twin_arginine_translocation.yaml
protein transport by the Tat complexGO:0043953
GO:0043953
protein transport by the Tat complex
GO:0043953 defines the biological process shared by TatA-, TatB-, and TatC-family components.
GO:0033281
TAT protein transport complex
GO:0033281 identifies the membrane complex formed by the Tat machinery.
PMID:23530902
The type II secretion system (Xcp) of Pseudomonas putida is active and involved in the secretion of phosphatases.
Primary research in P. putida KT2440 identifies two Tat gene clusters and shows that both complete systems can support transport of UxpB. This supports each complete system without assigning a distinct substrate repertoire to either locus.
Both Tat systems appeared to be capable of transporting the UxpB protein.
file:projects/P_PUTIDA/deep-research/PSEPK__bacterial_twin_arginine_translocation__ppu03070-deep-research-openscientist.md
OpenScientist module, pathway, and taxon review of bacterial twin-arginine translocation in Pseudomonas putida KT2440
The commissioned species-aware review found both P. putida KT2440 tatABC loci to satisfy the three roles and identified their primary KEGG assignment as protein export (ppu03060), distinct from downstream Xcp type II secretion in ppu03070.
https://data.pantherdb.org/ftp/sequence_classifications/19.0/PANTHER_Sequence_Classification_files/
PANTHER 19.0 sequence classifications
PANTHER's release-pinned sequence classifications (the source of the member index that module validation builds) place the E. coli K-12 and both P. putida KT2440 exemplars in PTHR30371:SF0 (TatC), PTHR33162:SF1 (TatB) and PTHR42982:SF1 (TatA).
PMID:11350936
Functional reconstitution of bacterial Tat translocation in vitro.
In vitro reconstitution with E. coli inner-membrane vesicles shows that Tat translocation needs TatA, TatB and TatC together and the membrane potential, but not ATP.
requires TatABC, an intact membrane potential and the twin-arginine targeting motif
PMID:19666509
Structural analysis of substrate binding by the TatBC component of the twin-arginine protein transport system.
Substrate binding to the TatBC receptor precedes TatA recruitment, the order modeled by this module.
In Escherichia coli substrate proteins initially bind to the integral membrane TatBC complex which then recruits the protein TatA to effect translocation.
PMID:29358647
Unanticipated functional diversity among the TatA-type components of the Tat protein translocase.
Distinct, non-interchangeable roles of TatC (signal-peptide docking), TatB (receptor organization) and TatA (translocation) in E. coli.
Despite their structural homology, TatA and TatB have distinct, non- interchangeable functions during Tat-dependent translocation.

The boundary starts with recognition of a folded Tat substrate and ends with membrane translocation. Cofactor loading and folding of substrates are upstream; signal-peptide cleavage and periplasmic destination functions are downstream. The module is species-neutral: the TatA, TatB and TatC families are conserved across bacteria and plastids, with E. coli K-12 as the experimentally characterized exemplar and P. putida KT2440 (two complete tatABC loci) as a second Gram-negative instance. Firmicutes such as Bacillus subtilis use minimal TatAC systems in which a TatA paralog also provides the TatB role; the B. subtilis TatA paralogs fall in PTHR42982:SF1 but inherit IBA rows from the TatB-clade PAINT node PTN002109144 (see the PTHR42982 family review). No B. subtilis exemplar is added because none has a gene review here. PTHR33162:SF1 also contains cyanobacterial and plastid TatA proteins, so the TatB receptor function is assigned to the TatB exemplars, not to the whole subfamily. GO describes the whole-transporter activity (GO:0009977) more readily than the separate TatA, TatB and TatC roles: the receptor annotons carry GO:0005048 signal sequence receptor activity and the transporter activity sits on the assembled-complex annoton, as in the member gene reviews. Those reviews record every subunit's 'enables GO:0009977' row, TatA included, as a qualifier defect (contributes_to): reconstituted transport needs TatA, TatB and TatC together, and the sources only hedge that TatA 'could' form the conduit (pore versus membrane weakening is unresolved). TatA's own activity is therefore a proposed term (Tat translocon conduit assembly activity) in its gene reviews, and the TatA unit carries no separate function here. In P. putida KT2440, PMID:23530902 shows that both complete systems can transport UxpB but does not establish locus-specific substrate repertoires.

4Nodes
3Parts
0Variant Sets
0Variants
3Annotons
2Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:bacterial_twin_arginine_translocation 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.

  • tatc_substrate_recognition → tata_translocation_assembly [NOT_CHECKED]
    TatC-dependent substrate recognition precedes recruitment of TatA into the active translocation assembly; this is not a metabolite chain.
  • tatb_receptor_organization → tata_translocation_assembly [NOT_CHECKED]
    TatB-dependent receptor organization precedes recruitment of TatA into the active translocation assembly; this is not a metabolite chain.

Function consistency and core coverage

6 gene-function check(s) reflected in core functions · 0 conflict(s) · 0 evidence or coverage gap(s) (9 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

AnnotonParticipantFunctionAssessment
tatc_family_component tatC (E. coli K-12)
UniProtKB:P69423
Family Representative 		signal sequence receptor activity
GO:0005048 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tatc_family_component tatC-I (P. putida KT2440)
UniProtKB:Q88P14
Family Representative 		signal sequence receptor activity
GO:0005048 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tatc_family_component tatC-II (P. putida KT2440)
UniProtKB:Q88D11
Family Representative 		signal sequence receptor activity
GO:0005048 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tatb_family_component tatB (E. coli K-12)
UniProtKB:P69425
Family Representative 		signal sequence receptor activity
GO:0005048 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tatb_family_component tatB-I (P. putida KT2440)
UniProtKB:Q88P13
Family Representative 		signal sequence receptor activity
GO:0005048 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tatb_family_component tatB (P. putida KT2440)
UniProtKB:Q88D12
Family Representative 		signal sequence receptor activity
GO:0005048 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
tatabc_transport_activity PROTEIN_COMPLEX
Gene 		proton motive force dependent protein transmembrane transporter activity
GO:0009977 		Participant Unchecked
No direct UniProt participant to compare. Abstract selectors and complex-wide activities cannot be inferred from donor or subunit gene reviews.
tatc_family_component TatC family
PANTHER:PTHR30371:SF0
Family 		signal sequence receptor activity
GO:0005048 		Family Supported
Family review supports GO:0005048 FAMILY_WIDE. Recognition of the twin-arginine signal peptide is the conserved TatC activity. This is a manual term assessment (no PAINT node asserts it); the E. coli and P. putida gene reviews propose it as NEW.
tatb_family_component TatB family
PANTHER:PTHR33162:SF1
Family 		signal sequence receptor activity
GO:0005048 		Family Supported
Family review supports GO:0005048 FAMILY_WIDE. Signal-peptide recognition by the TatBC receptor is the conserved activity of the TatB members. 154 of the 165 reviewed entries are in scope: 149 bacterial tatB in SF1, 4 plant TATB in SF3, and Synechocystis P73010. It is a manual term assessment; no PAINT node asserts it. The other 11 cyanobacterial and plastid TatA proteins in SF1 are listed as exceptions. P73010 (gene tatA1) is kept in scope because its 126-residue length is TatB-like, whereas the excepted cyanobacterial TatA proteins are 77 to 91 residues long.

Gene-review completeness (9/9 grounded genes reviewed)

9 complete review(s) · 1 with deep research · 0 missing review · 8 reviewed but lacking deep research

Gene Review Complete Deep research
tatA P69428 ✓ ✓ ✗
tatA-I Q88P12 ✓ ✓ ✗
tatA-II Q88D13 ✓ ✓ ✓
tatB P69425 ✓ ✓ ✗
tatB Q88D12 ✓ ✓ ✗
tatB-I Q88P13 ✓ ✓ ✗
tatC P69423 ✓ ✓ ✗
tatC-I Q88P14 ✓ ✓ ✗
tatC-II Q88D11 ✓ ✓ ✗

Details

Context
bacteriaNCBITaxon:2
plasma membraneGO:0005886
Bacterial twin-arginine protein translocationBiological Processbacterial_twin_arginine_translocation
protein transport by the Tat complexGO:0043953
Context
bacteriaNCBITaxon:2
plasma membraneGO:0005886

Connections

Part 1: Twin-arginine signal recognition and receptor scaffolding
TatC substrate recognitionBiological Processtatc_substrate_recognition

TatC provides the multispanning membrane scaffold that recognizes twin-arginine signal peptides together with TatB.

Annotons

TatC-family receptor component
tatc_family_component
Participant: Family: TatC family
Family:
TatC familyPANTHER:PTHR30371:SF0
Representative Members: tatC (E. coli K-12)UniProtKB:P69423 tatC-I (P. putida KT2440)UniProtKB:Q88P14 tatC-II (P. putida KT2440)UniProtKB:Q88D11

Function

signal sequence receptor activityGO:0005048
Substrates: twin-arginine signal peptide of a folded Tat precursor

Processes

protein transport by the Tat complexGO:0043953

Primary docking site for the twin-arginine signal peptide, directly recognizing the RR consensus motif; with TatB it forms the receptor that binds the folded precursor and provides binding sites for TatB and TatA.

PMID:29358647
TatC directly recognizes the RR consensus motif.
TatC functions as the primary docking site for the Tat signal peptide at the Tat translocase11,12 directly recognizing the RR-consensus motif13.
PMID:17212781
Substrate binding to TatBC depends on the signal peptide and is reduced by a TatC substitution.
Only variant Glu103Arg showed reduced copurification of SufI with TatBC.
Part 2: Tat receptor-complex organization
TatB receptor-complex organizationBiological Processtatb_receptor_organization

TatB associates 1:1 with TatC to organize the substrate receptor and couple substrate binding to TatA recruitment.

Annotons

TatB-family receptor component
tatb_family_component
Participant: Family: TatB family
Family:
TatB familyPANTHER:PTHR33162:SF1
Representative Members: tatB (E. coli K-12)UniProtKB:P69425 tatB-I (P. putida KT2440)UniProtKB:Q88P13 tatB (P. putida KT2440)UniProtKB:Q88D12

Function

signal sequence receptor activityGO:0005048
Substrates: twin-arginine signal peptide of a folded Tat precursor

Processes

protein transport by the Tat complexGO:0043953

Links TatC monomers into the circular receptor, contacts the signal peptide downstream of the RR motif and binds the folded mature domain of the precursor before TatA recruitment.

PMID:29358647
TatB contacts the signal peptide independently of the proton motive force.
TatB interacts with the Tat signal peptide downstream of the RR-consensus motif in a proton-motive force independent manner11,14,18.
PMID:11279240
TatB and TatC act as a structural and functional unit.
TatB and TatC act as a unit in both structural and functional terms
Part 3: Proton-motive-force-dependent translocation assembly
Active Tat translocon assemblyProtein Complextata_translocation_assembly

TatA is recruited to the substrate-bound TatBC receptor to form the dynamic, proton-motive-force-dependent translocon.

Annotons

Assembled TatABC protein-translocation activity
tatabc_transport_activity
Participant: Protein Complex: bacterial TatABC translocon
Protein Complex:
bacterial TatABC transloconGO:0033281
Active units:
TatA translocation subunit
Participant: Family: TatA family
Family:
TatA familyPANTHER:PTHR42982:SF1
Representative Members: tatA (E. coli K-12)UniProtKB:P69428 tatA-I (P. putida KT2440)UniProtKB:Q88P12 tatA-II (P. putida KT2440)UniProtKB:Q88D13
Role: Forms the recruited, dynamic membrane assembly required for folded-substrate passage.
TatB receptor subunit
Participant: Family: TatB family
Family:
TatB familyPANTHER:PTHR33162:SF1
Representative Members: tatB (E. coli K-12)UniProtKB:P69425 tatB-I (P. putida KT2440)UniProtKB:Q88P13 tatB (P. putida KT2440)UniProtKB:Q88D12
Role: Couples the substrate-bound receptor to TatA recruitment.
TatC receptor/scaffold subunit
Participant: Family: TatC family
Family:
TatC familyPANTHER:PTHR30371:SF0
Representative Members: tatC (E. coli K-12)UniProtKB:P69423 tatC-I (P. putida KT2440)UniProtKB:Q88P14 tatC-II (P. putida KT2440)UniProtKB:Q88D11
Role: Recognizes twin-arginine signal peptides with TatB.

Function

proton motive force dependent protein transmembrane transporter activityGO:0009977
Substrates: folded protein bearing a twin-arginine signal peptide
Products: translocated folded protein

Processes

protein transport by the Tat complexGO:0043953

The assembled TatABC machinery carries out membrane translocation after TatBC-dependent substrate recognition and TatA recruitment.

PMID:11350936
Assembled TatABC translocation requires the membrane potential.
requires TatABC, an intact membrane potential and the twin-arginine targeting motif