NaBBL_candidate_FOX1_4 is an additional BBL-family late oxidoreductase candidate in Nicotiana attenuata. The BBL family's role in late nicotine chemistry is now well supported, but FOX1_4 remains one of several unresolved attenuata paralogs.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005773
vacuole
|
IEA
GO_REF:0000044 |
KEEP AS NON CORE |
Summary: Vacuolar localization is plausible contextual information.
Reason: Retain the location while keeping the review focused on unresolved paralog identity within the BBL family.
|
|
GO:0016491
oxidoreductase activity
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: The parent oxidoreductase term is true but too broad.
Reason: BBL-family proteins are now linked to a specific late nicotine oxidation role rather than only generic redox chemistry.
Supporting Evidence:
file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-notes.md
The full preprint identifies BBLa/NicGS as the BBL-family enzyme responsible for stereoselective late-pathway oxidation in nicotine synthesis, so FOX1_4 remains a substantive BBL-like candidate rather than a generic flavoprotein bystander.
|
|
GO:0050660
flavin adenine dinucleotide binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: FAD binding is an appropriate annotation for this flavoprotein.
Reason: The BBL family is FAD linked, making this a useful and specific cofactor annotation.
|
|
GO:0071949
FAD binding
|
IEA
GO_REF:0000002 |
REMOVE |
Summary: This duplicates GO:0050660.
Reason: Keep the more explicit flavin adenine dinucleotide binding term and remove the redundant duplicate.
|
|
GO:0042179
nicotine biosynthetic process
|
IEA
GO_REF:0000041 |
KEEP AS NON CORE |
Summary: FOX1_4 is a plausible nicotine-pathway paralog but not a uniquely resolved one.
Reason: The pathway role of the BBL family is strong, yet the exact attenuata paralog assignment remains open.
Supporting Evidence:
file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-notes.md
The paper sharpens the biological role of the family but does not settle which current NICAT BBL paralog corresponds to the tobacco NicGS enzyme.
|
Q: Does FOX1_4 retain measurable late nicotine oxidase activity despite not being the leading BBL anchor?
Q: Is FOX1_4 expressed in the same root cell populations as the stronger BBL candidates?
Experiment: Test FOX1_4 in a reconstructed late-pathway assay alongside A622, UGT, and BGL components.
Hypothesis: FOX1_4 has weaker or partial BBL-like activity relative to the leading candidate.
Type: pathway reconstitution assay
Experiment: Compare FOX1_4 loss-of-function and multiplex BBL-family perturbations for effects on nicotine intermediates.
Hypothesis: FOX1_4 contributes redundantly within the BBL paralog set rather than acting as the sole late oxidase.
Type: comparative genetics plus metabolite profiling
The gene NaBBL_candidate_FOX1_4 in Nicotiana attenuata encodes a flavin-dependent oxidoreductase, as indicated by its UniProt accession number A0A1J6KZ94. This protein is characterized by domains such as the Berberine Bridge Enzyme (BBE) domain (IPR012951) and the FAD-binding PCMH-type domain (IPR016166), suggesting its involvement in oxidation-reduction processes.
Protein Family and Domains
Flavin-dependent oxidoreductases are a diverse group of enzymes that utilize flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN) as cofactors to catalyze redox reactions. The presence of the BBE domain in NaBBL_candidate_FOX1_4 suggests a structural and functional similarity to the berberine bridge enzyme family, which is known for its role in the biosynthesis of complex alkaloids. The FAD-binding PCMH-type domain indicates the protein's capacity to bind FAD, essential for its oxidoreductase activity.
Function and Biological Processes
While specific literature on NaBBL_candidate_FOX1_4 is limited, the structural domains provide insights into its potential function. Flavin-dependent oxidoreductases are involved in various biological processes, including the biosynthesis of secondary metabolites, detoxification, and catabolism. In plants, enzymes with BBE-like domains have been implicated in the formation of alkaloids and other specialized metabolites. For instance, the berberine bridge enzyme catalyzes the conversion of (S)-reticuline to (S)-scoulerine, a key step in the biosynthesis of benzylisoquinoline alkaloids. Therefore, it is plausible that NaBBL_candidate_FOX1_4 plays a role in similar biosynthetic pathways in Nicotiana attenuata.
Localization
The subcellular localization of flavin-dependent oxidoreductases can vary, but many are found in the cytoplasm or associated with organelles involved in metabolic processes. The specific localization of NaBBL_candidate_FOX1_4 in Nicotiana attenuata has not been experimentally determined.
Pathways and Substrate Specificity
Flavin-dependent oxidoreductases participate in a wide range of biochemical pathways, often involving the oxidation of substrates such as amines, alcohols, and sulfides. The substrate specificity of these enzymes is largely determined by their active site architecture and the presence of specific amino acid residues that interact with the substrate. Without direct studies on NaBBL_candidate_FOX1_4, its exact substrate and role in metabolic pathways remain speculative.
Inference from Structure and Evolution
The conservation of the BBE and FAD-binding domains across various species suggests that NaBBL_candidate_FOX1_4 may share functional characteristics with other flavin-dependent oxidoreductases. Comparative studies have shown that proteins with these domains are involved in oxidation-reduction reactions essential for the biosynthesis of secondary metabolites. For example, flavin-dependent monooxygenases catalyze the oxygenation of diverse substrates, contributing to the metabolic diversity observed in plants. (pubmed.ncbi.nlm.nih.gov)
Conclusion
In summary, while direct experimental evidence for NaBBL_candidate_FOX1_4 in Nicotiana attenuata is lacking, its domain architecture suggests a role as a flavin-dependent oxidoreductase, potentially involved in the biosynthesis of secondary metabolites such as alkaloids. Further studies, including gene expression analysis, substrate identification, and enzymatic assays, are necessary to elucidate its precise function, substrate specificity, and role within the plant's metabolic network.
id: A0A1J6KZ94
gene_symbol: NaBBL_candidate_FOX1_4
product_type: PROTEIN
status: DRAFT
aliases:
- FOX1_4
- NaBBL
taxon:
id: NCBITaxon:49451
label: Nicotiana attenuata
description: >-
NaBBL_candidate_FOX1_4 is an additional BBL-family late oxidoreductase candidate
in Nicotiana attenuata. The BBL family's role in late nicotine chemistry is now
well supported, but FOX1_4 remains one of several unresolved attenuata paralogs.
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings: []
- id: GO_REF:0000041
title: Gene Ontology annotation based on UniPathway vocabulary mapping
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
findings: []
- id: file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-uniprot.txt
title: UniProt entry A0A1J6KZ94 for Nicotiana attenuata FOX1_4
findings:
- statement: FOX1_4 is a BBL-family nicotine-associated oxidoreductase
supporting_text: Involved in the biosynthesis of pyridine alkaloid natural products, leading mainly to the production of anabasine, anatabine, nicotine and nornicotine ... Catalyzes a late oxidation step subsequent to the pyridine ring condensation reaction in the biosynthesis of alkaloids.
reference_section_type: DATABASE_ENTRY
- statement: UniProt places FOX1_4 in vacuole
supporting_text: 'CC -!- SUBCELLULAR LOCATION: Vacuole {ECO:0000256|ARBA:ARBA00004116}.'
reference_section_type: DATABASE_ENTRY
- id: file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-notes.md
title: NaBBL FOX1_4 candidate notes
findings:
- statement: The BBL family now has strong late-pathway support
supporting_text: The full preprint identifies BBLa/NicGS as the BBL-family enzyme responsible for stereoselective late-pathway oxidation in nicotine synthesis, so FOX1_4 remains a substantive BBL-like candidate rather than a generic flavoprotein bystander.
reference_section_type: LITERATURE_REVIEW
- statement: FOX1_4 is still an unresolved paralog rather than a settled primary copy
supporting_text: The paper sharpens the biological role of the family but does not settle which current NICAT BBL paralog corresponds to the tobacco NicGS enzyme.
reference_section_type: LITERATURE_REVIEW
existing_annotations:
- term:
id: GO:0005773
label: vacuole
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: Vacuolar localization is plausible contextual information.
action: KEEP_AS_NON_CORE
reason: >-
Retain the location while keeping the review focused on unresolved paralog
identity within the BBL family.
- term:
id: GO:0016491
label: oxidoreductase activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: The parent oxidoreductase term is true but too broad.
action: MARK_AS_OVER_ANNOTATED
reason: >-
BBL-family proteins are now linked to a specific late nicotine oxidation
role rather than only generic redox chemistry.
supported_by:
- reference_id: file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-notes.md
supporting_text: The full preprint identifies BBLa/NicGS as the BBL-family enzyme responsible for stereoselective late-pathway oxidation in nicotine synthesis, so FOX1_4 remains a substantive BBL-like candidate rather than a generic flavoprotein bystander.
reference_section_type: LITERATURE_REVIEW
- term:
id: GO:0050660
label: flavin adenine dinucleotide binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: FAD binding is an appropriate annotation for this flavoprotein.
action: ACCEPT
reason: >-
The BBL family is FAD linked, making this a useful and specific cofactor
annotation.
- term:
id: GO:0071949
label: FAD binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This duplicates GO:0050660.
action: REMOVE
reason: >-
Keep the more explicit flavin adenine dinucleotide binding term and remove
the redundant duplicate.
- term:
id: GO:0042179
label: nicotine biosynthetic process
evidence_type: IEA
original_reference_id: GO_REF:0000041
review:
summary: FOX1_4 is a plausible nicotine-pathway paralog but not a uniquely resolved one.
action: KEEP_AS_NON_CORE
reason: >-
The pathway role of the BBL family is strong, yet the exact attenuata
paralog assignment remains open.
supported_by:
- reference_id: file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-notes.md
supporting_text: The paper sharpens the biological role of the family but does not settle which current NICAT BBL paralog corresponds to the tobacco NicGS enzyme.
reference_section_type: LITERATURE_REVIEW
core_functions:
- molecular_function:
id: GO:0016491
label: oxidoreductase activity
directly_involved_in:
- id: GO:0042179
label: nicotine biosynthetic process
description: >-
FOX1_4 is a BBL-family FAD-linked oxidoreductase candidate for the late
nicotine-pathway oxidation step, but its exact position among the attenuata
BBL paralogs remains unresolved.
supported_by:
- reference_id: file:NICAT/NaBBL_candidate_FOX1_4/NaBBL_candidate_FOX1_4-notes.md
supporting_text: The full preprint identifies BBLa/NicGS as the BBL-family enzyme responsible for stereoselective late-pathway oxidation in nicotine synthesis, so FOX1_4 remains a substantive BBL-like candidate rather than a generic flavoprotein bystander.
reference_section_type: LITERATURE_REVIEW
proposed_new_terms: []
suggested_questions:
- question: Does FOX1_4 retain measurable late nicotine oxidase activity despite not being the leading BBL anchor?
- question: Is FOX1_4 expressed in the same root cell populations as the stronger BBL candidates?
suggested_experiments:
- description: Test FOX1_4 in a reconstructed late-pathway assay alongside A622, UGT, and BGL components.
experiment_type: pathway reconstitution assay
hypothesis: FOX1_4 has weaker or partial BBL-like activity relative to the leading candidate.
- description: Compare FOX1_4 loss-of-function and multiplex BBL-family perturbations for effects on nicotine intermediates.
experiment_type: comparative genetics plus metabolite profiling
hypothesis: FOX1_4 contributes redundantly within the BBL paralog set rather than acting as the sole late oxidase.