formate hydrogenlyase complex

cellstructuremech:formate_hydrogenlyase_complex · Energy complex · Multiprotein complex · Proposed

A membrane-bound Escherichia coli formate hydrogenlyase complex in which FdhF and HycB-HycG subunits couple formate oxidation to proton reduction, yielding carbon dioxide and hydrogen gas. [DOI:10.1038/s41467-022-32831-x]

Synonyms: FHL complex

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Formate dehydrogenase H	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	fdhF	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Formate-oxidizing molybdo-selenoprotein that donates electrons into the Hyc module. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 7 to UniProtKB:P07658 and describes it as Formate dehydrogenase H from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P07658/fdhF as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.
Formate hydrogenlyase subunit 2	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hycB	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Electron-transfer subunit in the membrane-bound Hyc module. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 3 to UniProtKB:P0AAK1 and describes it as Formate hydrogenlyase subunit 2 from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P0AAK1/hycB as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.
Formate hydrogenlyase subunit 3	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hycC	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Membrane subunit in the Hyc proton-reducing module. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 1 to UniProtKB:P16429 and describes it as Formate hydrogenlyase subunit 3 from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P16429/hycC as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.
Formate hydrogenlyase subunit 4	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hycD	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Membrane subunit in the Hyc proton-reducing module. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 6 to UniProtKB:P16430 and describes it as Formate hydrogenlyase subunit 4 from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P16430/hycD as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.
Formate hydrogenlyase subunit 5	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hycE	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Hydrogenase-3 large subunit in the Hyc module. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 2 to UniProtKB:P16431 and describes it as Formate hydrogenlyase subunit 5 from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P16431/hycE as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.
Formate hydrogenlyase subunit 6	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hycF	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Hyc module constituent resolved in the membrane-bound FHL structure. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 5 to UniProtKB:P16432 and describes it as Formate hydrogenlyase subunit 6 from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P16432/hycF as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.
Formate hydrogenlyase subunit 7	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hycG	1 copy in the E. coli K-12 PDB:7Z0T composite structure	ESSENTIAL	Hyc module constituent resolved in the membrane-bound FHL structure. `PDB:7Z0T` RCSB maps PDB:7Z0T entity 4 to UniProtKB:P16433 and describes it as Formate hydrogenlyase subunit 7 from E. coli K-12. `PMID:36104349` Steinhilper et al. 2022 resolved P16433/hycG as one of seven protein entities in the membrane-bound E. coli formate hydrogenlyase complex.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

Formate dehydrogenase H

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P07658`	Formate dehydrogenase H	fdhF	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P07658` Reviewed Swiss-Prot entry for E. coli K-12 fdhF matches the Formate dehydrogenase H accession mapped by RCSB to PDB:7Z0T entity 7.

Formate hydrogenlyase subunit 2

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0AAK1`	Formate hydrogenlyase subunit 2	hycB	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P0AAK1` Reviewed Swiss-Prot entry for E. coli K-12 hycB matches the Formate hydrogenlyase subunit 2 accession mapped by RCSB to PDB:7Z0T entity 3.

Formate hydrogenlyase subunit 3

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P16429`	Formate hydrogenlyase subunit 3	hycC	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P16429` Reviewed Swiss-Prot entry for E. coli K-12 hycC matches the Formate hydrogenlyase subunit 3 accession mapped by RCSB to PDB:7Z0T entity 1.

Formate hydrogenlyase subunit 4

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P16430`	Formate hydrogenlyase subunit 4	hycD	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P16430` Reviewed Swiss-Prot entry for E. coli K-12 hycD matches the Formate hydrogenlyase subunit 4 accession mapped by RCSB to PDB:7Z0T entity 6.

Formate hydrogenlyase subunit 5

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P16431`	Formate hydrogenlyase subunit 5	hycE	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P16431` Reviewed Swiss-Prot entry for E. coli K-12 hycE matches the Formate hydrogenlyase subunit 5 accession mapped by RCSB to PDB:7Z0T entity 2.

Formate hydrogenlyase subunit 6

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P16432`	Formate hydrogenlyase subunit 6	hycF	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P16432` Reviewed Swiss-Prot entry for E. coli K-12 hycF matches the Formate hydrogenlyase subunit 6 accession mapped by RCSB to PDB:7Z0T entity 5.

Formate hydrogenlyase subunit 7

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P16433`	Formate hydrogenlyase subunit 7	hycG	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) `UniProtKB:P16433` Reviewed Swiss-Prot entry for E. coli K-12 hycG matches the Formate hydrogenlyase subunit 7 accession mapped by RCSB to PDB:7Z0T entity 4.

Canonical examples

NCBITaxon:83333 Escherichia coli K-12 — Natural source of the FdhF/HycB-HycG formate hydrogenlyase complex deposited as the PDB:7Z0T composite cryo-EM structure. [PDB:7Z0T]

Functions

formate hydrogenlyase activity — The membrane-bound FHL complex oxidizes formate to carbon dioxide and transfers the released electrons through the Hyc module to reduce protons to molecular hydrogen.
- PMID:36104349 Steinhilper et al. 2022 describe E. coli FHL as a membrane-bound complex that couples formate oxidation by FdhF to proton reduction at the Hyc hydrogenase module.

Mechanism graphs

FHL couples formate oxidation to hydrogen evolution (FUNCTION)

The membrane-bound E. coli formate hydrogenlyase complex uses FdhF and the HycB-HycG module to transfer electrons from formate to protons.

Subject	Predicate	Object	Evidence
formate hydrogenlyase complex	enables	formate hydrogenlyase activity	`PMID:36104349` Steinhilper et al. 2022 resolved the membrane-bound E. coli FHL complex and described how it couples formate oxidation to hydrogen evolution.
formate	donates electrons to	Formate dehydrogenase H	`PMID:36104349` Steinhilper et al. 2022 place FdhF in the complex as the formate-oxidizing subunit.
Formate dehydrogenase H	feeds electrons to	HycB-HycG membrane hydrogenase module	`PDB:7Z0T` PDB:7Z0T resolves FdhF together with the six HycB-HycG protein entities in one composite structure.
formate hydrogenlyase activity	produces	CO2	`PMID:36104349`
formate hydrogenlyase activity	produces	H2	`PMID:36104349`

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral protein families for FdhF and HycB-HycG before replacing reviewed-label-only component rows. PDB:7Z0T and the reviewed E. coli UniProt records exactly identify the seven FHL proteins, but no InterPro, Pfam, or NCBIfam accession was verified as an exact source-neutral family for each named FHL subunit.

Evidence

PDB:7Z0T RCSB Protein Data Bank entry for the seven-protein E. coli formate hydrogenlyase composite cryo-EM structure.
GO:1990204 Gene Ontology cellular-component parent term for oxidoreductase complexes.
PMID:36104349 PubMed identifier for Steinhilper et al. 2022, Structure of the membrane-bound formate hydrogenlyase complex from Escherichia coli.
DOI:10.1038/s41467-022-32831-x DOI for the Steinhilper et al. 2022 E. coli formate hydrogenlyase paper.

Curation history

2026-10-02T06:16:01Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-02T06:17:13Z codex · EXPANDED_RECORD — Added GO parentage, FHL synonymy, reviewed-label-only FdhF and HycB-HycG component rows with E. coli K-12 UniProt examples, a PDB:7Z0T canonical example, formate hydrogenlyase activity, DOI/PMID/PDB evidence, a compact function graph, and a component-family grounding TODO.
2026-10-02T06:17:55Z codex · REVISED_TEXT — Restored standard Hyc and FHL capitalization in component role prose.

Source: data/structures/energy_complex/formate_hydrogenlyase_complex.yaml