Component

Human electron transfer flavoprotein / ETF

Mitochondrial ETFA-ETFB heterodimer with a single FAD; distinct from ETFDH.

4 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What it acts on

  1. Human ETF crystal structure places its single FAD in a cleft shared by ETFA and ETFB, with most FAD contacts in the alpha-chain C-terminal region.

    Human electron transfer flavoprotein / ETF → FAD source_derived_draftungraded
    Experimental context and source evidence
    evidence_spans
    [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMC26136", "locator": "HTML article p", "paragraph_index": 30, "char_start": 0, "char_end": 1354, "evidence_access": "full-text"}]
    experimental_model
    Recombinant human ETFA/ETFB expressed in E. coli and crystallized at 2.1 Angstrom resolution.
    exposure
    No nutrient intervention; structural or biochemical characterization.
    limitations
    Static structure; not a measurement of cellular cofactor availability.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Homo sapiens
    plain_language
    ETF is a two-protein electron shuttle carrying one B2-derived cofactor.
    primary_references
    [roberts-1996-human-etf] Three-dimensional structure of human electron transfer flavoprotein to 2.1-A resolution (1996). https://pubmed.ncbi.nlm.nih.gov/8962055/ DOI: 10.1073/pnas.93.25.14355
    tissue_or_cell_type
    Recombinant protein expressed in E. coli

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 728–739

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant human ETFA/ETFB expressed in E. coli and crystallized at 2.1 Angstrom resolution. · source_derived_draft · unverified_draft

    ### b2-met-human-etf-fad-heterodimer Human ETF crystal structure places its single FAD in a cleft shared by ETFA and ETFB, with most FAD contacts in the alpha-chain C-terminal region. Condition category: normal nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: ETF is a two-protein electron shuttle carrying one B2-derived cofactor. organism: Homo sapiens tissue_or_cell_type: Recombinant protein expressed in E. coli experimental_model: Recombinant human ETFA/ETFB expressed in E. coli and crystallized at 2.1 Angstrom resolution. limitations: Static structure; not a measurement of cellular cofactor availability. exposure: No nutrient intervention; structural or biochemical characterization. evidence_spans: [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMC26136", "locator": "HTML article p", "paragraph_index": 30, "char_start": 0, "char_end": 1354, "evidence_access": "full-text"}] [roberts-1996-human-etf] Three-dimensional structure of human electron transfer flavoprotein to 2.1-A resolution (1996). https://pubmed.ncbi.nlm.nih.gov/8962055/ DOI: 10.1073/pnas.93.25.14355
    Complete structured claim and evidence

What acts on it

  1. Human MCAD and ETF form an electron-transfer complex in which a recognition loop anchors binding while the ETF FAD domain samples electron-transfer-compatible conformations.

    Human medium-chain acyl-CoA dehydrogenase / ACADM → Human electron transfer flavoprotein / ETF source_derived_draftungraded
    Experimental context and source evidence
    evidence_spans
    [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMID15159392", "locator": "metadata.abstractText", "paragraph_index": 0, "char_start": 0, "char_end": 1430, "evidence_access": "primary-abstract"}]
    experimental_model
    Human ETF-MCAD complex crystallography and solution interfacial mutagenesis.
    exposure
    No nutrient intervention; structural or biochemical characterization.
    limitations
    Primary abstract supports mechanism; no inference about clinical MCAD supplementation response.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Homo sapiens
    plain_language
    Fatty-acid oxidation hands electrons from MCAD to a distinct ETF carrier.
    primary_references
    [toogood-2004-etf-mcad] Extensive domain motion and electron transfer in the human electron transferring flavoprotein.medium chain Acyl-CoA dehydrogenase complex (2004). https://pubmed.ncbi.nlm.nih.gov/15159392/ DOI: 10.1074/jbc.m404884200
    tissue_or_cell_type
    Recombinant human protein complex

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 741–752

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human ETF-MCAD complex crystallography and solution interfacial mutagenesis. · source_derived_draft · unverified_draft

    ### b2-met-mcad-etf-electron-transfer Human MCAD and ETF form an electron-transfer complex in which a recognition loop anchors binding while the ETF FAD domain samples electron-transfer-compatible conformations. Condition category: normal nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Fatty-acid oxidation hands electrons from MCAD to a distinct ETF carrier. organism: Homo sapiens tissue_or_cell_type: Recombinant human protein complex experimental_model: Human ETF-MCAD complex crystallography and solution interfacial mutagenesis. limitations: Primary abstract supports mechanism; no inference about clinical MCAD supplementation response. exposure: No nutrient intervention; structural or biochemical characterization. evidence_spans: [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMID15159392", "locator": "metadata.abstractText", "paragraph_index": 0, "char_start": 0, "char_end": 1430, "evidence_access": "primary-abstract"}] [toogood-2004-etf-mcad] Extensive domain motion and electron transfer in the human electron transferring flavoprotein.medium chain Acyl-CoA dehydrogenase complex (2004). https://pubmed.ncbi.nlm.nih.gov/15159392/ DOI: 10.1074/jbc.m404884200
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Selective effects of ETF-QO FAD-site mutations supported electron entry from ETF through the [4Fe-4S] center, followed by flavin-mediated transfer to ubiquinone.

    Rhodobacter sphaeroides ETF-QO → [4Fe-4S] iron-sulfur cluster source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    Direct mechanistic integration of an iron-containing center with B2-derived FAD.
    evidence_spans
    [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMC3106343", "locator": "HTML article p", "paragraph_index": 51, "char_start": 0, "char_end": 1197, "evidence_access": "full-text"}]
    experimental_model
    Recombinant Rhodobacter sphaeroides ETF-QO; human ETF and MCAD in mixed-species reconstitution; mutagenesis and EPR.
    exposure
    No nutrient intervention; structural or biochemical characterization.
    limitations
    Mechanistic inference from mutagenesis/EPR and activity; no dietary iron or B2 intervention.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Rhodobacter sphaeroides; human ETF/MCAD reagents
    plain_language
    ETF-QO uses its iron-sulfur center and flavin for different stages of the electron relay.
    primary_references
    [swanson-2008-etf-qo] The iron-sulfur cluster of electron transfer flavoprotein-ubiquinone oxidoreductase is the electron acceptor for electron transfer flavoprotein (2008). https://pubmed.ncbi.nlm.nih.gov/18672901/ DOI: 10.1021/bi800507p
    tissue_or_cell_type
    Purified proteins

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 794–806

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant Rhodobacter sphaeroides ETF-QO; human ETF and MCAD in mixed-species reconstitution; mutagenesis and EPR. · source_derived_draft · unverified_draft

    ### b2-met-etf-qo-iron-sulfur-entry Selective effects of ETF-QO FAD-site mutations supported electron entry from ETF through the [4Fe-4S] center, followed by flavin-mediated transfer to ubiquinone. Condition category: normal nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: ETF-QO uses its iron-sulfur center and flavin for different stages of the electron relay. organism: Rhodobacter sphaeroides; human ETF/MCAD reagents tissue_or_cell_type: Purified proteins experimental_model: Recombinant Rhodobacter sphaeroides ETF-QO; human ETF and MCAD in mixed-species reconstitution; mutagenesis and EPR. limitations: Mechanistic inference from mutagenesis/EPR and activity; no dietary iron or B2 intervention. exposure: No nutrient intervention; structural or biochemical characterization. cross_nutrient: Direct mechanistic integration of an iron-containing center with B2-derived FAD. evidence_spans: [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMC3106343", "locator": "HTML article p", "paragraph_index": 51, "char_start": 0, "char_end": 1197, "evidence_access": "full-text"}] [swanson-2008-etf-qo] The iron-sulfur cluster of electron transfer flavoprotein-ubiquinone oxidoreductase is the electron acceptor for electron transfer flavoprotein (2008). https://pubmed.ncbi.nlm.nih.gov/18672901/ DOI: 10.1021/bi800507p
    Complete structured claim and evidence

  2. Interface mutagenesis and solution electron-transfer measurements supported a role for MCAD Glu212 and ETF alpha Arg249 interactions in productive electron transfer.

    Human medium-chain acyl-CoA dehydrogenase / ACADM → Human electron transfer flavoprotein alpha / ETFA source_derived_draftungraded
    Experimental context and source evidence
    evidence_spans
    [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMID15159392", "locator": "metadata.abstractText", "paragraph_index": 0, "char_start": 0, "char_end": 1430, "evidence_access": "primary-abstract"}]
    experimental_model
    Human ETF-MCAD complex crystallography and solution interfacial mutagenesis.
    exposure
    No nutrient intervention; structural or biochemical characterization.
    limitations
    Residue interactions were inferred from combined structural/kinetic evidence; this is not a dietary-deficiency experiment.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Homo sapiens
    plain_language
    Correct contact between the proteins matters as well as having the cofactor.
    primary_references
    [toogood-2004-etf-mcad] Extensive domain motion and electron transfer in the human electron transferring flavoprotein.medium chain Acyl-CoA dehydrogenase complex (2004). https://pubmed.ncbi.nlm.nih.gov/15159392/ DOI: 10.1074/jbc.m404884200
    tissue_or_cell_type
    Recombinant protein interaction assays

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 754–765

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human ETF-MCAD complex crystallography and solution interfacial mutagenesis. · source_derived_draft · unverified_draft

    ### b2-met-mcad-etf-interface Interface mutagenesis and solution electron-transfer measurements supported a role for MCAD Glu212 and ETF alpha Arg249 interactions in productive electron transfer. Condition category: normal nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Correct contact between the proteins matters as well as having the cofactor. organism: Homo sapiens tissue_or_cell_type: Recombinant protein interaction assays experimental_model: Human ETF-MCAD complex crystallography and solution interfacial mutagenesis. limitations: Residue interactions were inferred from combined structural/kinetic evidence; this is not a dietary-deficiency experiment. exposure: No nutrient intervention; structural or biochemical characterization. evidence_spans: [{"source_bundle": "artifacts/riboflavin_metabolism_sources.json", "source_key": "PMID15159392", "locator": "metadata.abstractText", "paragraph_index": 0, "char_start": 0, "char_end": 1430, "evidence_access": "primary-abstract"}] [toogood-2004-etf-mcad] Extensive domain motion and electron transfer in the human electron transferring flavoprotein.medium chain Acyl-CoA dehydrogenase complex (2004). https://pubmed.ncbi.nlm.nih.gov/15159392/ DOI: 10.1074/jbc.m404884200
    Complete structured claim and evidence

In the sources

Preserved passages that mention this component, quoted exactly. Open one to read it in context.

    This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.

    Evidence, AI assistance and curation standards