TAT protein transport complex

GO:0033281 · Secretion system · Multiprotein complex · Proposed

A complex of three proteins integral to the cytoplasmic membrane of bacteria and membranes of organelles derived from bacteria (chloroplasts and mitochondria) involved in membrane transport of folded proteins. [GO:0033281]

Synonyms: Tat translocase; twin-arginine translocation complex; TatABC complex

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
TatA-family translocation component	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	tatA	ESSENTIAL	Oligomeric membrane component recruited by substrate-bound receptor complexes to form the active Tat transport site. `DOI:10.1038/s41564-026-02399-z` Deme et al. 2026 structurally resolved early Escherichia coli TatABC states containing TatA bound to substrate-loaded TatBC. `DOI:10.1021/bi500169s` Behrendt and Bruser 2014 characterized the transition from E. coli TatBC receptor complexes to substrate-bound TatABC complexes.
TatC-family receptor component	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	tatC	ESSENTIAL	Core membrane receptor component that recognizes twin-arginine signal peptides and nucleates substrate-bound Tat translocase assembly. `DOI:10.1038/s41564-026-02399-z` Deme et al. 2026 resolved the TatC contacts that recognize the twin-arginine targeting sequence in bacterial TatBC and TatABC core complexes.
TatB-family receptor component	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	tatB	ESSENTIAL	Receptor subunit in three-component Tat systems that cooperates with TatC to bind signal peptides before TatA recruitment. `DOI:10.1038/s41564-026-02399-z` Deme et al. 2026 resolved E. coli TatBC receptor and TatABC complexes in resting and substrate-bound states. `DOI:10.1021/bi500169s` Behrendt and Bruser 2014 biochemically characterized the E. coli TatBC complex and its substrate-triggered shift toward TatABC.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Three-component TatABC protein-transport complexes occur in many bacteria, but Tat systems are absent from some bacteria and simplified to two-component TatAC machines in some Gram-positive lineages. [DOI:10.1038/nrmicro2814]

Canonical examples

NCBITaxon:562 Escherichia coli — Reference three-component TatABC system used for bacterial TatBC and TatABC core-complex structural studies. [DOI:10.1038/s41564-026-02399-z]

Functions

protein transport by the Tat complex GO:0043953 — The Tat complex moves folded twin-arginine-signal-bearing substrates across an energized cytoplasmic membrane.
- GO:0043953 GO:0043953 defines folded-protein transport across bacterial cytoplasmic membranes or membranes of bacteria-derived organelles by the TAT complex.
- DOI:10.1038/nrmicro2814 Palmer and Berks 2012 review the bacterial Tat pathway as an export route for folded proteins.

Mechanism graphs

TatBC recognizes folded cargo and recruits TatA (FUNCTION)

In three-component bacterial Tat systems, TatB and TatC form a membrane receptor that recognizes a folded substrate's twin-arginine signal peptide, recruits TatA-family protomers, and forms a proton-motive-force dependent transport site.

Subject	Predicate	Object	Evidence
TatC-family receptor component	binds targeting motif on	folded twin-arginine substrate	`DOI:10.1038/s41564-026-02399-z` Deme et al. 2026 structurally mapped the bacterial TatC contacts with Tat signal-peptide targeting sequences.
TatB-family receptor component	clamps	folded twin-arginine substrate	`DOI:10.1038/s41564-026-02399-z` Deme et al. 2026 resolved TatB positions around Tat-bound signal peptides in substrate-loaded E. coli Tat core complexes.
TatC-family receptor component	assembles with	TatB-family receptor component	`DOI:10.1021/bi500169s` Behrendt and Bruser 2014 characterized the E. coli TatBC complex and its conversion toward a substrate-bound TatABC assembly.
folded twin-arginine substrate	triggers recruitment of	TatA-family translocation component	`DOI:10.1038/s41564-026-02399-z` Deme et al. 2026 captured early substrate-bound TatABC states and model TatA recruitment after substrate binding.
TatA-family translocation component	completes	TAT protein transport complex	`DOI:10.1007/s10930-019-09859-y` Frain et al. 2019 review the TatA assembly step that follows cargo recognition by the Tat receptor.
proton motive force	powers	protein transport by the Tat complex	`DOI:10.1038/nrmicro2814` Palmer and Berks 2012 review energy coupling and folded protein movement by the bacterial Tat pathway.
TAT protein transport complex	carries out	protein transport by the Tat complex	`GO:0043953` GO:0043953 defines protein transport by the Tat complex as folded-protein movement across the relevant membrane by the TAT complex.

Discussions

CURATION_TODO (RESOLVED): Do two-component Gram-positive TatAC translocases belong in this GO:0033281 TAT protein transport complex record? Bacillus subtilis TatAdCd and TatAyCy are named, minimal two-component translocases whose bifunctional TatA-family proteins fill the receptor role handled by TatB in E. coli-like TatABC complexes.

Evidence

DOI:10.1038/nrmicro2814 Palmer and Berks 2012, The twin-arginine translocation (Tat) protein export pathway, Nature Reviews Microbiology.
DOI:10.1007/s10930-019-09859-y Frain et al. 2019, Transport of Folded Proteins by the Tat System.
DOI:10.1021/bi500169s Behrendt and Bruser 2014, The TatBC Complex of the Tat Protein Translocase in Escherichia coli and Its Transition to the Substrate-Bound TatABC Complex, Biochemistry.
DOI:10.1038/s41564-026-02399-z Deme et al. 2026, Structure and substrate recognition by the bacterial twin-arginine translocation (Tat) core complex, Nature Microbiology.

Curation history

2026-09-06T20:18:45Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-06T20:20:25Z claude · EXPANDED_RECORD — Added Tat translocase synonymy, protein-complex parentage, TatA, TatB, and TatC components, bacterial and archaeal taxonomic scope, Escherichia coli and Bacillus subtilis canonical examples, GO:0043953 protein transport function grounding, record evidence, and a TatBC-TatA substrate-recognition graph.
2026-09-06T20:22:01Z claude · REVIEW_FIX — Resolved issue #216 by scoping the GO:0033281 record to three-component TatABC systems, making TatB essential in that boundary, removing Bacillus minimal TatAC and archaeal taxonomic assertions, and recording the TatAC boundary as a resolved discussion.

Source: data/structures/secretion_system/tat_protein_transport_complex.yaml