sodium-translocating NADH:quinone reductase complex

GO:0160292 · Energy complex · Multiprotein complex · Proposed

Sodium-translocating NADH:quinone reductase complex is a bacterial respiratory-chain protein complex composed of NqrA, NqrB, NqrC, NqrD, NqrE, and NqrF that transfers electrons from NADH to ubiquinone while exporting sodium ions across the cytoplasmic membrane. [GO:0160292]

Synonyms: Na+-NQR complex; Na(+)-translocating NADH-quinone reductase 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
Na(+)-translocating NADH-quinone reductase subunit A	Protein	part of	`InterPro:IPR008703`	nqrA	ESSENTIAL	NqrA constituent of the six-subunit sodium-pumping NADH:quinone oxidoreductase. `InterPro:IPR008703` InterPro IPR008703 is a family entry named Na(+)-translocating NADH-quinone reductase subunit A. `PDB:7XK3` RCSB maps PDB:7XK3 polymer entity 1 to Vibrio cholerae O395 Na(+)-translocating NADH-quinone reductase subunit A, UniProtKB:A5F5X1.
Na(+)-translocating NADH-quinone reductase subunit B	Protein	part of	`InterPro:IPR010966`	nqrB	ESSENTIAL	Hydrophobic, FMN-binding NqrB constituent of the six-subunit sodium-pumping complex. `InterPro:IPR010966` InterPro IPR010966 is a family entry named Na(+)-translocating NADH-quinone reductase subunit B. `PDB:7XK3` RCSB maps PDB:7XK3 polymer entity 2 to Vibrio cholerae O395 Na(+)-translocating NADH-quinone reductase subunit B, UniProtKB:A5F5X0.
Na(+)-translocating NADH-quinone reductase subunit C	Protein	part of	`InterPro:IPR010204`	nqrC	ESSENTIAL	FMN-binding NqrC constituent of the six-subunit sodium-pumping complex. `InterPro:IPR010204` InterPro IPR010204 is a family entry named Na(+)-translocating NADH-quinone reductase subunit C. `PDB:7XK3` RCSB maps PDB:7XK3 polymer entity 3 to Vibrio cholerae O395 Na(+)-translocating NADH-quinone reductase subunit C, UniProtKB:A5F5Y7.
Na(+)-translocating NADH-quinone reductase subunit D	Protein	part of	`InterPro:IPR011292`	nqrD	ESSENTIAL	Membrane NqrD constituent of the six-subunit sodium-pumping complex. `InterPro:IPR011292` InterPro IPR011292 is a family entry named Na(+)-translocating NADH-quinone reductase subunit D. `PDB:7XK3` RCSB maps PDB:7XK3 polymer entity 4 to Vibrio cholerae O395 Na(+)-translocating NADH-quinone reductase subunit D, UniProtKB:A5F5Y6.
Na(+)-translocating NADH-quinone reductase subunit E	Protein	part of	`InterPro:IPR010967`	nqrE	ESSENTIAL	Membrane NqrE constituent of the six-subunit sodium-pumping complex. `InterPro:IPR010967` InterPro IPR010967 is a family entry named Na(+)-translocating NADH-quinone reductase subunit E. `PDB:7XK3` RCSB maps PDB:7XK3 polymer entity 5 to Vibrio cholerae O395 Na(+)-translocating NADH-quinone reductase subunit E, UniProtKB:A5F5Y5.
Na(+)-translocating NADH-quinone reductase subunit F	Protein	part of	`InterPro:IPR010205`	nqrF	ESSENTIAL	NqrF constituent of the complex that carries FAD and an iron-sulfur center. `InterPro:IPR010205` InterPro IPR010205 is a family entry named Na(+)-translocating NADH-quinone reductase subunit F; its GO annotations include FAD binding and 2 iron, 2 sulfur cluster binding, matching the NqrF cofactor role. `PDB:7XK3` RCSB maps PDB:7XK3 polymer entity 6 to Vibrio cholerae O395 Na(+)-translocating NADH-quinone reductase subunit F, UniProtKB:A5F5Y4.

Canonical examples

NCBITaxon:345073 Vibrio cholerae O395 — Vibrio cholerae O395 supplied the nqrA-nqrF gene-source sequences for the cryo-EM Na+-NQR structure deposited as PDB:7XK3. [PDB:7XK3]

Functions

sodium-pumping NADH:quinone oxidoreductase activity — Na+-NQR couples electron transfer from NADH to ubiquinone with export of sodium ions from the cytoplasm toward the periplasm.
- GO:0160292 GO:0160292 defines the complex as the bacterial NqrABCDEF protein complex that couples NADH-to-ubiquinone electron transfer to sodium-ion transport from cytoplasm to periplasm.
- PDB:7XK3 RCSB annotates all six PDB:7XK3 polymer entities with EC 7.2.1.1, NADH:ubiquinone reductase (Na+-transporting).
- DOI:10.1038/s41467-022-31718-1 Kishikawa et al. 2022 solved Vibrio cholerae Na+-NQR cryo-EM structures and describe the enzyme as coupling NADH-to-ubiquinone electron transfer with Na+ pumping.

Mechanism graphs

Na+-NQR couples NADH oxidation to sodium export (FUNCTION)

The sodium-translocating NADH:quinone reductase complex reduces ubiquinone with NADH-derived electrons while moving sodium ions from the cytoplasm toward the periplasm.

Subject	Predicate	Object	Evidence
sodium-translocating NADH:quinone reductase complex	enables	sodium-pumping NADH:quinone oxidoreductase activity	`GO:0160292` GO:0160292 defines the NqrABCDEF complex by this coupled redox and transport activity.
NADH	donates electrons to	sodium-pumping NADH:quinone oxidoreductase activity	`GO:0160292` GO:0160292 states that the complex catalyzes electron transfer from NADH.
ubiquinone	accepts electrons in	sodium-pumping NADH:quinone oxidoreductase activity	`GO:0160292` GO:0160292 states that the complex transfers NADH-derived electrons to ubiquinone.
sodium-pumping NADH:quinone oxidoreductase activity	produces	ubiquinol	`DOI:10.1038/s41467-022-31718-1` Kishikawa et al. 2022 describe Na+-NQR as a NADH-ubiquinone oxidoreductase.
sodium-pumping NADH:quinone oxidoreductase activity	exports	sodium ion	`GO:0160292` GO:0160292 states that electron transfer is coupled to transport of sodium ions from the cytoplasm to the periplasm.
sodium-pumping NADH:quinone oxidoreductase activity	contributes to	transmembrane sodium motive force	`DOI:10.1038/s41467-022-31718-1` Kishikawa et al. 2022 describe Na+-NQR as generating an electrochemical Na+ gradient through coupled Na+ pumping.

Evidence

GO:0160292 Gene Ontology cellular-component term for the bacterial sodium-translocating NADH:quinone reductase complex.
GO:0098803 Gene Ontology cellular-component term for respiratory-chain protein complexes.
InterPro:IPR008703 InterPro family for Na+-NQR subunit A.
InterPro:IPR010966 InterPro family for Na+-NQR subunit B.
InterPro:IPR010204 InterPro family for Na+-NQR subunit C.
InterPro:IPR011292 InterPro family for Na+-NQR subunit D.
InterPro:IPR010967 InterPro family for Na+-NQR subunit E.
InterPro:IPR010205 InterPro family for Na+-NQR subunit F.
DOI:10.1038/s41467-022-31718-1 Kishikawa et al. 2022, Cryo-EM structures of Na+-pumping NADH-ubiquinone oxidoreductase from Vibrio cholerae, Nature Communications.
PMID:35882843 PubMed identifier for Kishikawa et al. 2022 as reported by RCSB PDB:7XK3 and PubMed.
PMID:38955304 PubMed identifier for the Steuber and Fritz 2024 Na+-NQR review cited by the GO:0160292 definition.
PDB:7XK3 RCSB Protein Data Bank entry for a Vibrio cholerae O395 six-subunit Na+-NQR cryo-EM structure from Kishikawa et al. 2022.

Curation history

2026-09-24T07:40:43Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-24T07:42:02Z codex · EXPANDED_RECORD — Added GO synonymy and respiratory-chain parentage, six NqrA-F constituent components grounded to exact InterPro families and PDB:7XK3 polymer entities, a Vibrio cholerae O395 canonical example, Na+-pumping NADH:quinone oxidoreductase function evidence, and a compact whole-enzyme redox-to-sodium coupling graph.
2026-09-24T07:55:48Z codex · ADDRESS_REVIEW — #1466/#1467: moved the sodium-motive-force graph edge from the exported sodium ion to the sodium-pumping activity and expanded the InterPro:IPR010205 NqrF evidence note to cite its FAD-binding and 2Fe-2S-binding GO annotations.

Source: data/structures/energy_complex/sodium_translocating_nadh_quinone_reductase_complex.yaml