NaBBL2_candidate_FOX1_2 is a BBL-like oxidoreductase candidate for the late nicotine pathway in Nicotiana attenuata. BBL-family participation in the stereoselective late pathway is strongly supported, and FOX1_2 remains a leading candidate for the attenuata BBL2-like copy.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005773
vacuole
|
IEA
GO_REF:0000044 |
KEEP AS NON CORE |
Summary: Vacuolar localization is plausible and worth retaining as non-core context.
Reason: UniProt supports a vacuolar location, but the key curation signal is the catalytic late-pathway role rather than compartment detail.
Supporting Evidence:
file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-uniprot.txt
CC -!- SUBCELLULAR LOCATION: Vacuole {ECO:0000256|ARBA:ARBA00004116}.
|
|
GO:0016491
oxidoreductase activity
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: This generic oxidoreductase term is true but underspecific.
Reason: The BBL family is now tied to a specific late nicotine oxidase role, so the parent term is not the most informative curation outcome.
Supporting Evidence:
file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-notes.md
The full preprint makes BBLa/NicGS a mechanistically defined late-pathway enzyme that drives stereoselective nicotine formation, with both structural and dropout support.
|
|
GO:0050660
flavin adenine dinucleotide binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: FAD binding is an appropriate cofactor annotation for FOX1_2.
Reason: BBL-family proteins are FAD-linked oxidoreductases, and this cofactor term is informative and specific.
|
|
GO:0071949
FAD binding
|
IEA
GO_REF:0000002 |
REMOVE |
Summary: This is redundant with GO:0050660.
Reason: Keep GO:0050660 as the preferred cofactor-binding annotation and drop the duplicate variant.
|
|
GO:0042179
nicotine biosynthetic process
|
IEA
GO_REF:0000041 |
ACCEPT |
Summary: This is an appropriate core pathway annotation for FOX1_2.
Reason: FOX1_2 is the best current attenuata BBL2-like anchor, and the BBL family is now directly supported as a core late nicotine-pathway module.
Supporting Evidence:
file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-notes.md
That strengthens the existing choice to keep FOX1_2 as the best current BBL2-like anchor, while still leaving exact NICAT BBL paralog resolution open.
|
Q: Does FOX1_2 perform the same substrate-specific NicGS chemistry inferred for the tobacco BBL ortholog?
Q: Are the remaining BBL-family paralogs partially redundant with FOX1_2 or functionally divergent?
Experiment: Reconstitute the late nicotine pathway with FOX1_2 and assay stereoselective formation of nicotine glucoside and nicotine.
Hypothesis: FOX1_2 is the principal attenuata BBL/NicGS paralog.
Type: pathway reconstitution assay
Experiment: Profile nicotine stereochemistry and glucosylated intermediates after targeted FOX1_2 disruption.
Hypothesis: Loss of FOX1_2 will substantially impair the stereoselective late nicotine step.
Type: genetics plus chiral metabolite profiling
The gene NaBBL2_candidate_FOX1_2 in Nicotiana attenuata encodes a flavin-dependent oxidoreductase, as indicated by its UniProt accession number A0A1J6KPK0. This protein is characterized by several conserved domains, including the Berberine Bridge Enzyme (BBE) domain (IPR012951) and the FAD-binding PCMH-type domains (IPR016166, IPR036318, IPR016167, IPR016169), suggesting its role in oxidation-reduction processes.
Protein Function and Catalytic Activity
Flavin-dependent oxidoreductases are enzymes that utilize flavin adenine dinucleotide (FAD) as a cofactor to catalyze redox reactions. The presence of the BBE domain in NaBBL2_candidate_FOX1_2 suggests a function similar to that of berberine bridge enzymes, which are known to catalyze the formation of complex alkaloids through oxidative coupling reactions. In plants, such enzymes are often involved in the biosynthesis of secondary metabolites, including alkaloids, which play roles in defense mechanisms and other physiological processes.
Biological Processes and Localization
While specific experimental data on NaBBL2_candidate_FOX1_2 are limited, the structural domains present in the protein provide insights into its potential biological roles. The BBE domain is commonly associated with enzymes involved in the biosynthesis of alkaloids and other secondary metabolites. Additionally, the FAD-binding domains are indicative of a role in redox reactions, possibly linked to metabolic pathways involving electron transfer.
In Nicotiana attenuata, flavin-dependent oxidoreductases have been implicated in various metabolic processes. For instance, a related flavin-dependent oxidoreductase, identified as A0A1J6IW50, has been associated with alkaloid metabolism and localized to the vacuole, suggesting a compartmentalized role in secondary metabolite biosynthesis (db.cngb.org). Given the structural similarities, it is plausible that NaBBL2_candidate_FOX1_2 functions in a comparable manner, contributing to the biosynthesis or modification of alkaloid compounds within specific cellular compartments.
Pathway Involvement
The specific metabolic pathways involving NaBBL2_candidate_FOX1_2 have not been explicitly characterized. However, based on its domain architecture and the known functions of similar enzymes, it is reasonable to infer that this protein participates in the biosynthetic pathways of secondary metabolites, particularly alkaloids. These pathways are crucial for plant defense and adaptation, as alkaloids often serve as deterrents against herbivores and pathogens.
Inference from Structure and Evolution
The conservation of the BBE and FAD-binding domains across various plant species suggests an evolutionary conserved function in secondary metabolism. The BBE domain, in particular, is associated with enzymes that catalyze oxidative reactions leading to the formation of complex alkaloid structures. The presence of these domains in NaBBL2_candidate_FOX1_2 indicates that it likely shares a similar catalytic mechanism and functional role.
Conclusion
While direct experimental evidence regarding the function of NaBBL2_candidate_FOX1_2 in Nicotiana attenuata is currently lacking, the analysis of its conserved domains strongly suggests that it acts as a flavin-dependent oxidoreductase involved in the biosynthesis of alkaloid compounds. Its activity is likely compartmentalized within specific cellular structures, such as the vacuole, to facilitate the production and storage of these secondary metabolites. Further experimental studies are necessary to elucidate the precise substrates, reaction mechanisms, and regulatory pathways associated with this enzyme.
The YAML description field was revised to keep it as a standalone biological summary. Project-specific curation framing moved here instead.
id: A0A1J6KPK0
gene_symbol: NaBBL2_candidate_FOX1_2
product_type: PROTEIN
status: DRAFT
aliases:
- FOX1_2
- NaBBL2
taxon:
id: NCBITaxon:49451
label: Nicotiana attenuata
description: >-
NaBBL2_candidate_FOX1_2 is a BBL-like oxidoreductase candidate for the late nicotine pathway in
Nicotiana attenuata. BBL-family participation in the stereoselective late pathway is strongly
supported, and FOX1_2 remains a leading candidate for the attenuata BBL2-like copy.
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/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-uniprot.txt
title: UniProt entry A0A1J6KPK0 for Nicotiana attenuata FOX1_2
findings:
- statement: FOX1_2 is a BBL-family late oxidase associated with nicotine biosynthesis
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 assigns FOX1_2 to vacuole and FAD-dependent chemistry
supporting_text: 'CC -!- SUBCELLULAR LOCATION: Vacuole {ECO:0000256|ARBA:ARBA00004116}.'
reference_section_type: DATABASE_ENTRY
- id: file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-notes.md
title: NaBBL2 FOX1_2 candidate notes
findings:
- statement: The glucosylation paper mechanistically secures BBL-family late-pathway chemistry
supporting_text: The full preprint makes BBLa/NicGS a mechanistically defined late-pathway enzyme that drives stereoselective nicotine formation, with both structural and dropout support.
reference_section_type: LITERATURE_REVIEW
- statement: FOX1_2 is the best current BBL2-like anchor in the project
supporting_text: That strengthens the existing choice to keep FOX1_2 as the best current BBL2-like anchor, while still leaving exact NICAT BBL paralog resolution open.
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 and worth retaining as non-core context.
action: KEEP_AS_NON_CORE
reason: >-
UniProt supports a vacuolar location, but the key curation signal is the
catalytic late-pathway role rather than compartment detail.
supported_by:
- reference_id: file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-uniprot.txt
supporting_text: 'CC -!- SUBCELLULAR LOCATION: Vacuole {ECO:0000256|ARBA:ARBA00004116}.'
reference_section_type: DATABASE_ENTRY
- term:
id: GO:0016491
label: oxidoreductase activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This generic oxidoreductase term is true but underspecific.
action: MARK_AS_OVER_ANNOTATED
reason: >-
The BBL family is now tied to a specific late nicotine oxidase role, so the
parent term is not the most informative curation outcome.
supported_by:
- reference_id: file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-notes.md
supporting_text: The full preprint makes BBLa/NicGS a mechanistically defined late-pathway enzyme that drives stereoselective nicotine formation, with both structural and dropout support.
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 cofactor annotation for FOX1_2.
action: ACCEPT
reason: >-
BBL-family proteins are FAD-linked oxidoreductases, and this cofactor term
is informative and specific.
- term:
id: GO:0071949
label: FAD binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This is redundant with GO:0050660.
action: REMOVE
reason: >-
Keep GO:0050660 as the preferred cofactor-binding annotation and drop the
duplicate variant.
- term:
id: GO:0042179
label: nicotine biosynthetic process
evidence_type: IEA
original_reference_id: GO_REF:0000041
review:
summary: This is an appropriate core pathway annotation for FOX1_2.
action: ACCEPT
reason: >-
FOX1_2 is the best current attenuata BBL2-like anchor, and the BBL family is
now directly supported as a core late nicotine-pathway module.
supported_by:
- reference_id: file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-notes.md
supporting_text: That strengthens the existing choice to keep FOX1_2 as the best current BBL2-like anchor, while still leaving exact NICAT BBL paralog resolution open.
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_2 is the best current NICAT BBL2-like oxidoreductase candidate for the
late stereoselective nicotine-pathway oxidation step.
supported_by:
- reference_id: file:NICAT/NaBBL2_candidate_FOX1_2/NaBBL2_candidate_FOX1_2-notes.md
supporting_text: The full preprint makes BBLa/NicGS a mechanistically defined late-pathway enzyme that drives stereoselective nicotine formation, with both structural and dropout support.
reference_section_type: LITERATURE_REVIEW
proposed_new_terms: []
suggested_questions:
- question: Does FOX1_2 perform the same substrate-specific NicGS chemistry inferred for the tobacco BBL ortholog?
- question: Are the remaining BBL-family paralogs partially redundant with FOX1_2 or functionally divergent?
suggested_experiments:
- description: Reconstitute the late nicotine pathway with FOX1_2 and assay stereoselective formation of nicotine glucoside and nicotine.
experiment_type: pathway reconstitution assay
hypothesis: FOX1_2 is the principal attenuata BBL/NicGS paralog.
- description: Profile nicotine stereochemistry and glucosylated intermediates after targeted FOX1_2 disruption.
experiment_type: genetics plus chiral metabolite profiling
hypothesis: Loss of FOX1_2 will substantially impair the stereoselective late nicotine step.