Component

Rat TXNRD1 Sec498Cys protein

Engineered replacement of the C-terminal selenium-containing residue in rat Txnrd1 by cysteine.

3 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. Engineered rat TXNRD1 terminal mutants retained one FAD per subunit and rapidly formed a thiolate-flavin charge-transfer signal upon NADPH titration.

    Rat TXNRD1 Sec498Cys protein → FAD source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    Distinct B2-cofactor and selenium-site functions cannot substitute for one another.
    evidence_location
    Abstract
    experimental_model
    Rat TXNRD1 Sec498Cys, Sec498Ser and C-terminal truncation expressed in E. coli; FAD analysis, NADPH titration and thioredoxin assays.
    exposure
    Purified-enzyme assay
    limitations
    Includes Sec498Cys, Sec498Ser and terminal truncation; engineered proteins, not nutrient-depleted animals.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Rattus norvegicus protein expressed in Escherichia coli
    plain_language
    A defective terminal center can leave upstream flavin reduction intact.
    primary_references
    [zhong2000] Essential role of selenium in the catalytic activities of mammalian thioredoxin reductase revealed by characterization of recombinant enzymes with selenocysteine mutations. (2000). https://pubmed.ncbi.nlm.nih.gov/10849437/ DOI: 10.1074/jbc.m000690200
    tissue_or_cell_type
    Purified recombinant enzyme; no intact tissue
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1374–1386

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Rat TXNRD1 Sec498Cys, Sec498Ser and C-terminal truncation expressed in E. coli; FAD analysis, NADPH titration and thioredoxin assays. · source_derived_draft · unverified_draft

    ### b2-txnrd-mutants-upstream-retained Engineered rat TXNRD1 terminal mutants retained one FAD per subunit and rapidly formed a thiolate-flavin charge-transfer signal upon NADPH titration. Condition category: machinery_impairment nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: A defective terminal center can leave upstream flavin reduction intact. organism: Rattus norvegicus protein expressed in Escherichia coli tissue_or_cell_type: Purified recombinant enzyme; no intact tissue experimental_model: Rat TXNRD1 Sec498Cys, Sec498Ser and C-terminal truncation expressed in E. coli; FAD analysis, NADPH titration and thioredoxin assays. limitations: Includes Sec498Cys, Sec498Ser and terminal truncation; engineered proteins, not nutrient-depleted animals. exposure: Purified-enzyme assay cross_nutrient: Distinct B2-cofactor and selenium-site functions cannot substitute for one another. evidence_location: Abstract [zhong2000] Essential role of selenium in the catalytic activities of mammalian thioredoxin reductase revealed by characterization of recombinant enzymes with selenocysteine mutations. (2000). https://pubmed.ncbi.nlm.nih.gov/10849437/ DOI: 10.1074/jbc.m000690200
    Complete structured claim and evidence

  2. Replacing rat TXNRD1 Sec498 with cysteine lowered thioredoxin-reduction kcat about 100-fold; serine substitution and terminal truncation lacked detectable activity.

    Rat TXNRD1 Sec498Cys protein → Thioredoxin proteins source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    B2-derived FAD cannot replace the selenium-containing catalytic residue.
    evidence_location
    Abstract
    experimental_model
    Rat TXNRD1 Sec498Cys, Sec498Ser and C-terminal truncation expressed in E. coli; FAD analysis, NADPH titration and thioredoxin assays.
    exposure
    Purified-enzyme assay
    limitations
    Assay-substrate species is unresolved in accessible source details; engineered proteins do not establish dietary B2-by-selenium synergy.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Rattus norvegicus protein expressed in Escherichia coli
    plain_language
    Flavin retention did not preserve efficient thioredoxin reduction.
    primary_references
    [zhong2000] Essential role of selenium in the catalytic activities of mammalian thioredoxin reductase revealed by characterization of recombinant enzymes with selenocysteine mutations. (2000). https://pubmed.ncbi.nlm.nih.gov/10849437/ DOI: 10.1074/jbc.m000690200
    tissue_or_cell_type
    Purified recombinant enzyme; no intact tissue
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1388–1400

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Rat TXNRD1 Sec498Cys, Sec498Ser and C-terminal truncation expressed in E. coli; FAD analysis, NADPH titration and thioredoxin assays. · source_derived_draft · unverified_draft

    ### b2-txnrd-sec498cys-turnover Replacing rat TXNRD1 Sec498 with cysteine lowered thioredoxin-reduction kcat about 100-fold; serine substitution and terminal truncation lacked detectable activity. Condition category: machinery_impairment nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Flavin retention did not preserve efficient thioredoxin reduction. organism: Rattus norvegicus protein expressed in Escherichia coli tissue_or_cell_type: Purified recombinant enzyme; no intact tissue experimental_model: Rat TXNRD1 Sec498Cys, Sec498Ser and C-terminal truncation expressed in E. coli; FAD analysis, NADPH titration and thioredoxin assays. limitations: Assay-substrate species is unresolved in accessible source details; engineered proteins do not establish dietary B2-by-selenium synergy. exposure: Purified-enzyme assay cross_nutrient: B2-derived FAD cannot replace the selenium-containing catalytic residue. evidence_location: Abstract [zhong2000] Essential role of selenium in the catalytic activities of mammalian thioredoxin reductase revealed by characterization of recombinant enzymes with selenocysteine mutations. (2000). https://pubmed.ncbi.nlm.nih.gov/10849437/ DOI: 10.1074/jbc.m000690200
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. The rat TXNRD1 Sec498Cys structure showed conserved FAD- and NADPH-binding architecture around the N-terminal redox center.

    FAD → Rat thioredoxin reductase 1 / Txnrd1 source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    B2-FAD and nicotinamide cofactors provide the upstream side of a selenium-containing reductase.
    evidence_location
    Abstract
    experimental_model
    Rat TXNRD1 Sec498Cys recombinant mutant with NADP+, 3.0-A crystallography and substrate-docking interpretation.
    exposure
    Purified-enzyme assay
    limitations
    Structure used a Sec-to-Cys mutant and oxidized NADP+; direct atom-level conclusions about wild-type selenium chemistry are limited.
    nutrient_topic
    Riboflavin research collection; topical membership is not evidence of a direct dietary effect. · Riboflavin (vitamin B2)
    organism
    Rattus norvegicus protein expressed recombinantly
    plain_language
    Thioredoxin reductase has a flavin input side.
    primary_references
    [sandalova2001] Three-dimensional structure of a mammalian thioredoxin reductase: implications for mechanism and evolution of a selenocysteine-dependent enzyme. (2001). https://pubmed.ncbi.nlm.nih.gov/11481439/ DOI: 10.1073/pnas.171178698
    tissue_or_cell_type
    Purified recombinant enzyme; no intact tissue

    Riboflavin: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1346–1358

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Rat TXNRD1 Sec498Cys recombinant mutant with NADP+, 3.0-A crystallography and substrate-docking interpretation. · source_derived_draft · unverified_draft

    ### b2-txnrd1-fad-nadph-architecture The rat TXNRD1 Sec498Cys structure showed conserved FAD- and NADPH-binding architecture around the N-terminal redox center. Condition category: normal nutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Thioredoxin reductase has a flavin input side. organism: Rattus norvegicus protein expressed recombinantly tissue_or_cell_type: Purified recombinant enzyme; no intact tissue experimental_model: Rat TXNRD1 Sec498Cys recombinant mutant with NADP+, 3.0-A crystallography and substrate-docking interpretation. limitations: Structure used a Sec-to-Cys mutant and oxidized NADP+; direct atom-level conclusions about wild-type selenium chemistry are limited. exposure: Purified-enzyme assay cross_nutrient: B2-FAD and nicotinamide cofactors provide the upstream side of a selenium-containing reductase. evidence_location: Abstract [sandalova2001] Three-dimensional structure of a mammalian thioredoxin reductase: implications for mechanism and evolution of a selenocysteine-dependent enzyme. (2001). https://pubmed.ncbi.nlm.nih.gov/11481439/ DOI: 10.1073/pnas.171178698
    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