tripartite ATP-independent periplasmic transporter complex

GO:0031317 · Other · Multiprotein complex · Proposed

A complex consisting of two membrane proteins and one extracytoplasmic solute receptor. Such transporters transport a variety of substrates without direct ATP power, instead using energy from ion gradients. [GO:0031317]

Synonyms: TRAP transporter complex; TRAP-T transporter complex

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

Components

Component	Type	Part of / acts on	Grounding	Role
TRAP extracytoplasmic solute receptor	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	Binds substrate outside the cytoplasmic membrane and delivers it to the DctQ/DctM-type membrane transporter. `GO:0031317` GO:0031317 defines the TRAP transporter complex as containing one extracytoplasmic solute receptor. `DOI:10.1128/JB.179.17.5482-5493.1997` Forward et al. 1997 identified DctP as the periplasmic C4-dicarboxylate-binding component of the Rhodobacter capsulatus DctPQM TRAP transporter.
TRAP transporter, small membrane protein DctQ	Protein	part of	`InterPro:IPR007387`	Small integral membrane constituent of DctPQM-type TRAP transporters. `GO:0031317` GO:0031317 defines the TRAP transporter complex as containing two membrane proteins. `InterPro:IPR007387` InterPro:IPR007387 covers TRAP transporter small membrane proteins of the DctQ family. `DOI:10.1128/JB.179.17.5482-5493.1997` Forward et al. 1997 identified R. capsulatus dctQ as a membrane-protein gene required with dctP and dctM for functional C4-dicarboxylate transport.
TRAP transporter large membrane protein DctM	Protein	part of	`InterPro:IPR004681`	Large integral membrane constituent of DctPQM-type TRAP transporters. `GO:0031317` GO:0031317 defines the TRAP transporter complex as containing two membrane proteins. `InterPro:IPR004681` InterPro:IPR004681 covers TRAP transporter large membrane proteins of the DctM family. `DOI:10.1128/JB.179.17.5482-5493.1997` Forward et al. 1997 identified R. capsulatus dctM as a membrane-protein gene required with dctP and dctQ for functional C4-dicarboxylate transport.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: TRAP transporter complexes occur in bacteria but are not universal across the bacterial domain. [DOI:10.1111/j.1574-6976.2010.00236.x]
NCBITaxon:2157 Archaea — VARIABLE: TRAP transporter complexes have been detected in archaea but are not universal across the archaeal domain. [DOI:10.1111/j.1574-6976.2010.00236.x]

Canonical examples

NCBITaxon:1061 Rhodobacter capsulatus — R. capsulatus DctPQM is the founding C4-dicarboxylate TRAP transporter complex characterized genetically and bioenergetically. [DOI:10.1128/JB.179.17.5482-5493.1997]

Functions

ion-gradient-dependent solute uptake — Couples extracytoplasmic receptor binding to secondary active solute import without direct ATP hydrolysis.
- GO:0031317 GO:0031317 defines TRAP transporter complexes by transport of varied substrates without direct ATP power and with energy from ion gradients.
- DOI:10.1128/JB.179.17.5482-5493.1997 Forward et al. 1997 found that R. capsulatus DctPQM succinate uptake tracked membrane potential rather than ATP abundance.

Discussions

CURATION_TODO (OPEN): Resolve an exact source-neutral family grounding for the extracytoplasmic solute receptor class of TRAP transporter complexes. The first record uses a reviewed receptor-class label rather than forcing all TRAP extracytoplasmic receptors into either the DctP InterPro family or the TAXI-family branch.

Evidence

GO:0031317 GO:0031317 is an active cellular-component term for the tripartite ATP-independent periplasmic transporter complex and is_a GO:1990351 transporter complex.
DOI:10.1128/JB.179.17.5482-5493.1997 Forward et al. 1997 characterized the R. capsulatus dctPQM genes, showed that dctP, dctQ, and dctM were sufficient for C4-dicarboxylate transport, and proposed the TRAP transporter name.
DOI:10.1099/00221287-145-12-3431 Rabus et al. 1999 analyzed TRAP transporters as an ancient family of extracytoplasmic solute-receptor-dependent secondary active transporters.
DOI:10.1111/j.1574-6976.2010.00236.x Mulligan, Fischer and Thomas 2011 reviewed tripartite ATP-independent periplasmic transporters in bacteria and archaea.

Curation history

2026-10-01T16:25:59Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-01T16:27:13Z codex · EXPANDED_RECORD — Added GO synonymy, transporter-complex parentage, TRAP receptor and membrane components, bacterial and archaeal taxonomy, the R. capsulatus DctPQM canonical example, ion-gradient-dependent transport function, evidence, and a receptor-grounding discussion.

Source: data/structures/other/tripartite_atp_independent_periplasmic_transporter_complex.yaml