GSTF6

Summary: GSTF6 was detected by mass spectrometry in a purified vegetative vacuole proteome.

Reason: GSTF6 is a soluble GST with no targeting peptide and is cytosolic. A single detection in an organelle proteome, without targeted validation, most likely reflects carry-over of an abundant stress-induced cytosolic protein. There is no evidence that GSTF6 acts in the vacuole. The deep research specifically warns against transferring the vacuolar-transport role of TT19/GSTF12 to GSTF6.

Summary: Phylogenetic inference of glutathione transferase activity across the GST family, including the Arabidopsis phi-class members.

Reason: GSTF6 is a phi-class GST with conserved glutathione-binding residues. Recombinant GSTF6 is soluble and catalyses glutathione conjugation. This is the core molecular function of the protein. The IBA node placement is consistent with the experimental data.

Summary: Electronic mapping from EC 2.5.1.18 / RHEA:16437 to glutathione transferase activity.

Reason: The mapping is correct. GSTF6 catalyses glutathione conjugation, as shown by experiment. This is the core molecular function.

Summary: GSTF6 was retained on a copper-immobilized metal affinity chromatography (Cu-IMAC) column in a root proteomic survey.

Reason: Retention on an IMAC resin shows that the protein has surface residues (typically His clusters) that can coordinate an immobilized metal. It does not show that the protein binds copper as part of its biological function. GSTF6 is not a known metalloprotein, and no copper site or copper-dependent activity has been described. The annotation records an assay property rather than a molecular function.

Summary: GSTF6 was detected in a membrane-fraction protein correlation profiling dataset.

Reason: GSTF6 has no signal peptide and is cytosolic. The source study profiled membrane-associated protein complexes after cell fractionation, which is not a suitable assay for assigning an extracellular location. Extracellular action of GSTF6 has not been established.

Summary: Phylogenetic inference that phi-class GSTs act in the cytoplasm.

Reason: GSTF6 is a soluble GST without targeting signals. Cytoplasm is correct, and cytosol is the more specific location.

Summary: Author statement in the Arabidopsis GST family survey that phi GSTs are cytoplasmic.

Reason: This agrees with the absence of targeting peptides and the soluble nature of the recombinant protein. It is consistent with the IBA and the cytosol annotations.

Summary: GSTF6 was detected in purified mitochondria from oxidatively stressed Arabidopsis cell cultures.

Reason: The authors themselves note that several stress-induced proteins in their fraction are generally considered extramitochondrial. GSTF6 has no mitochondrial targeting peptide and is strongly induced by H2O2. Its detection most likely reflects association or contamination of an abundant cytosolic protein, not a mitochondrial location.

Summary: GSTF6 was detected in a large LC-MS/MS mitochondrial proteome.

Reason: GSTF6 lacks a mitochondrial presequence. Only about half of the proteins in this experimental set are predicted to be mitochondrial, so the dataset includes non-mitochondrial proteins. No targeted study places GSTF6 in mitochondria.

Summary: GSTF6 was identified in the crude cytosolic fraction of Arabidopsis leaves by size exclusion chromatography and LC-MS profiling.

Reason: This agrees with GSTF6 having no targeting peptide and with its soluble behaviour. The cytosol is the expected site of action, including for any contribution to the cytosolic glutathione-conjugate steps of camalexin biosynthesis.

Summary: UniProt subcellular location (Cytoplasm, cytosol) mapped to GO.

Reason: Consistent with the HDA cytosol annotation and with GSTF6 having no targeting peptide.

Summary: Phylogenetic inference that GST family members take part in glutathione metabolism.

Reason: GSTF6 uses reduced glutathione as a co-substrate to form S-glutathione conjugates. For camalexin, the conjugate (GS-IAN) is processed further by GGP1/GGP3, so conjugate formation is a direct step of glutathione metabolism. The term is broad, but it is the right level for a GST whose specific physiological substrates are uncertain.

Summary: Expression-based annotation. A stress-inducible GST transcript was induced by the oxidative-stress-inducing herbicide acifluorfen, alongside the Trp pathway and camalexin.

Reason: GSTF6 is reliably induced by oxidative stress (H2O2, acifluorfen). IEP shows that its expression responds to the stress, not that GSTF6 carries out the response. Combined RNAi of GSTF6/7/9/10 gave only subtle changes. The annotation is reasonable as a non-core expression response.

Summary: ARBA machine-learning inference that GSTs act in toxin catabolism.

Reason: Glutathione conjugation of xenobiotic electrophiles, including herbicides, is a well-established general role of plant GSTs. GSTF6 is induced by herbicides and safeners and has conjugating activity. However, no specific toxin has been shown to be detoxified by GSTF6 in planta, and its activity on the model substrate CDNB is low. This is a plausible family-level role, not a demonstrated core function.

Summary: Author statement from the Arabidopsis GST family survey linking GSTs to herbicide detoxification.

Reason: The statement is about the GST family in general, and GSTF6 was shown to be herbicide-inducible and catalytically active. A GSTF6-specific toxin substrate has not been identified, so this is kept as non-core.

Summary: ERD11 (GSTF6) was isolated as a dehydration-inducible cDNA.

Reason: The paper directly shows dehydration-induced expression. It does not show a role for GSTF6 in drought tolerance, so this is a non-core expression response.

Summary: GSTF6 was detected in a MudPIT proteome of purified cell walls from suspension cells.

Reason: GSTF6 lacks a signal peptide, and the study itself relied on signal peptide prediction to select genuine extracellular proteins. A soluble cytosolic GST found in a wall preparation is best treated as a contaminant.

Summary: GSTF6 was detected in the plasmodesmal proteome of Arabidopsis suspension cells.

Reason: The authors estimate that about a third of the PD-proteome consists of cytoplasmic contaminants. GSTF6 is an abundant, stress-induced cytosolic GST that has not been validated at plasmodesmata.

Summary: AtSubP sequence-based prediction of chloroplast localization.

Reason: GSTF6 has no chloroplast transit peptide. It is described as lacking targeting peptides and is found in the cytosolic fraction. This computational prediction is contradicted by sequence and experimental localization data.

Summary: GSTF6 was identified among proteins co-purifying with Rbp47b-GFP-marked stress granules after heat stress.

Reason: Stress granules form in the cytosol, so this is compatible with the cytosolic location of GSTF6. The authors note that many non-canonical SG proteins are enzymes that may be stored in SGs during stress. This is a plausible condition-specific location, but it is not part of GSTF6's core function.

Summary: Phylogenetic inference of glutathione binding in the phi GST clade. GSTF6 (AT1G02930) is among the donors because of its own experimental annotation.

Reason: GSTF6 binds glutathione through its N-terminal G-site, and this binding is part of its glutathione transferase activity. The protein was experimentally retained on glutathione affinity media. The target appearing among the IBA donors reflects that experimental evidence, not circularity.

Summary: GSTF6 was purified from Arabidopsis cell culture by glutathione-affinity chromatography.

Reason: Retention on immobilized glutathione is direct evidence of glutathione binding. This fits the G-site of a phi GST and underlies its transferase activity.

Summary: GSTs including GSTF6 changed in abundance in the Arabidopsis root proteome after Cd2+ exposure.

Reason: Cadmium induction of GSTF6 is also reported independently (UniProt INDUCTION). This is an expression response to a stress, not a demonstrated role in cadmium tolerance.

Summary: GSTF6 was retained on Co2+-charged IMAC resin in a survey of metal-interacting mitochondrial proteins.

Reason: As for copper, IMAC retention shows surface residues that coordinate an immobilized metal, not a biological cobalt-binding function. GSTF6 is also not a mitochondrial protein. No cobalt-dependent function of GSTF6 is known.

Summary: The source paper screened Arabidopsis phi GSTs for natural-product ligands. The abstract attributes selective camalexin binding to GSTF2.

Reason: The cached abstract restricts heterocyclic-ligand binding "uniquely" to GSTF2 and GSTF3, and attributes camalexin and quercetin-3-O-rhamnoside (quercitrin) binding to GSTF2. In the GSTF nomenclature co-authored by the same group (Wagner, Edwards, Dixon & Mauch 2002, PMID:12090627, as recorded in UniProt), GSTF3 is At2g02930 (Q9SLM6), a different gene from GSTF6 (At1g02930, P42760), which carries only the legacy alias "AtGSTF3". A QuickGO query for PMID:21631432 (recorded in GSTF6-notes.md) returns the camalexin and quercitrin binding IDA annotations for GSTF2 (P46422) and GSTF6 (P42760) but none for Q9SLM6, which is the pattern expected if the paper's "GSTF3" was mapped to P42760 through that legacy alias. Whichever of GSTF2/GSTF3 the full text attributes the binding to, it is not GSTF6, and the abstract's "uniquely" wording excludes binding by the other GSTFs screened. The full text could not be read (it is not in PMC, and Portland Press and the Durham repository returned 403), so this rests on the abstract's explicit statement plus the nomenclature evidence, not on data the curator saw for GSTF6. Because the full text could not be read, CLAUDE.md requires UNDECIDED rather than REMOVE for an experimental row: the alias evidence points strongly to a name-collision mis-mapping, which TAIR should be asked to check against the full text. Camalexin binding is not biologically implausible for GSTF6, which is itself implicated in camalexin biosynthesis (GS-IAN formation); the mis-mapping concern rests on the abstract's "uniquely ... GSTF2 and GSTF3" wording and the alias collision, not on biology.

Summary: Same source as the camalexin binding annotation. The abstract attributes quercetin-3-O-rhamnoside binding to GSTF2.

Reason: The cached abstract restricts heterocyclic-ligand binding "uniquely" to GSTF2 and GSTF3, and attributes camalexin and quercetin-3-O-rhamnoside (quercitrin) binding to GSTF2. In the GSTF nomenclature co-authored by the same group (Wagner, Edwards, Dixon & Mauch 2002, PMID:12090627, as recorded in UniProt), GSTF3 is At2g02930 (Q9SLM6), a different gene from GSTF6 (At1g02930, P42760), which carries only the legacy alias "AtGSTF3". A QuickGO query for PMID:21631432 (recorded in GSTF6-notes.md) returns the camalexin and quercitrin binding IDA annotations for GSTF2 (P46422) and GSTF6 (P42760) but none for Q9SLM6, which is the pattern expected if the paper's "GSTF3" was mapped to P42760 through that legacy alias. Whichever of GSTF2/GSTF3 the full text attributes the binding to, it is not GSTF6, and the abstract's "uniquely" wording excludes binding by the other GSTFs screened. The full text could not be read (it is not in PMC, and Portland Press and the Durham repository returned 403), so this rests on the abstract's explicit statement plus the nomenclature evidence, not on data the curator saw for GSTF6. Because the full text could not be read, CLAUDE.md requires UNDECIDED rather than REMOVE for an experimental row: the alias evidence points strongly to a name-collision mis-mapping, which TAIR should be asked to check against the full text.