--- provider: openscientist model: openscientist-autonomous cached: false start_time: '2026-07-08T12:48:42.889622' end_time: '2026-07-08T13:12:36.300142' duration_seconds: 1433.41 template_file: templates/gene_hypothesis_deep_research.md template_variables: organism: ORYSJ gene: Q6YYC5 gene_symbol: Q6YYC5 uniprot_accession: Q6YYC5 taxon_id: NCBITaxon:39947 taxon_label: Oryza sativa subsp. japonica focus_type: computational_prediction hypothesis_slug: prediction-k63-linked-ubiquitination hypothesis_text: ProtNLM2 predicts that the Oryza sativa (japonica) protein Q6YYC5 catalyzes protein K63-linked ubiquitination (GO:0070534), a linkage-specific refinement of its existing generic GO:0016567 (protein ubiquitination) annotation. Its Arabidopsis ortholog RGLG2 (a RING-domain E3 ligase) assembles K63-linked polyubiquitin chains. Independently assess whether Q6YYC5 has the domain architecture of a functional RGLG-family E3 ubiquitin ligase (a catalytic RING-type zinc-finger domain, plus any vWA or other RGLG-characteristic domains) and whether orthology to K63-chain-forming RGLG enzymes supports the K63-linkage-specific refinement, or whether the linkage specificity cannot be determined from sequence. term_context: '- Term: protein K63-linked ubiquitination (GO:0070534)' reference_context: No specific reference context supplied. source_file: '' source_selector: '' source_context_yaml: "hypothesis: ProtNLM2 predicts that the Oryza sativa (japonica)\ \ protein Q6YYC5 catalyzes protein K63-linked\n ubiquitination (GO:0070534),\ \ a linkage-specific refinement of its existing generic GO:0016567 (protein\n\ \ ubiquitination) annotation. Its Arabidopsis ortholog RGLG2 (a RING-domain E3\ \ ligase) assembles K63-linked\n polyubiquitin chains. Independently assess whether\ \ Q6YYC5 has the domain architecture of a functional\n RGLG-family E3 ubiquitin\ \ ligase (a catalytic RING-type zinc-finger domain, plus any vWA or other RGLG-characteristic\n\ \ domains) and whether orthology to K63-chain-forming RGLG enzymes supports the\ \ K63-linkage-specific refinement,\n or whether the linkage specificity cannot\ \ be determined from sequence.\nfocus_type: computational_prediction\nterm_id:\ \ GO:0070534\nterm_label: protein K63-linked ubiquitination\ncontext: []\nreference_id:\ \ []" provider_config: timeout: 3600 max_retries: 3 parameters: allowed_domains: [] max_iterations: 3 use_hypotheses: false investigation_mode: autonomous poll_interval: 30 timeout: 7200 save_artifacts: true artifact_max_bytes: 5242880 citation_count: 11 artifact_count: 5 artifact_sources: openscientist_artifacts_zip: 5 artifacts: - filename: artifacts_Q6YYC5_GO_decision_table.csv path: openscientist_artifacts/artifacts_Q6YYC5_GO_decision_table.csv media_type: text/csv source: openscientist_artifacts_zip data_storage_id: null description: OpenScientist Q6YYC5 GO decision table - filename: artifacts_Q6YYC5_RGLG_distance_matrix.csv path: openscientist_artifacts/artifacts_Q6YYC5_RGLG_distance_matrix.csv media_type: text/csv source: openscientist_artifacts_zip data_storage_id: null description: OpenScientist Q6YYC5 RGLG distance matrix - filename: artifacts_Q6YYC5_evidence_matrix.csv path: openscientist_artifacts/artifacts_Q6YYC5_evidence_matrix.csv media_type: text/csv source: openscientist_artifacts_zip data_storage_id: null description: OpenScientist Q6YYC5 evidence matrix - filename: final_report.html path: openscientist_artifacts/final_report.html media_type: text/html source: openscientist_artifacts_zip data_storage_id: null description: OpenScientist final report - filename: final_report.pdf path: openscientist_artifacts/final_report.pdf media_type: application/pdf source: openscientist_artifacts_zip data_storage_id: null description: OpenScientist final report --- ## Question # AIGR Gene Hypothesis Deep Research You are evaluating one focused gene curation hypothesis for AI Gene Review. This is not a general gene overview. Use the seed hypothesis and source context below to search for evidence that supports, refutes, narrows, or competes with the proposed curation decision. ## Target Gene - **Organism code:** ORYSJ - **Taxon:** Oryza sativa subsp. japonica (NCBITaxon:39947) - **Gene directory:** Q6YYC5 - **Gene symbol:** Q6YYC5 - **UniProt accession:** Q6YYC5 ## Focus - **Focus type:** computational_prediction - **Hypothesis slug:** prediction-k63-linked-ubiquitination - **Source file:** - **Source selector:** ## Seed Hypothesis ProtNLM2 predicts that the Oryza sativa (japonica) protein Q6YYC5 catalyzes protein K63-linked ubiquitination (GO:0070534), a linkage-specific refinement of its existing generic GO:0016567 (protein ubiquitination) annotation. Its Arabidopsis ortholog RGLG2 (a RING-domain E3 ligase) assembles K63-linked polyubiquitin chains. Independently assess whether Q6YYC5 has the domain architecture of a functional RGLG-family E3 ubiquitin ligase (a catalytic RING-type zinc-finger domain, plus any vWA or other RGLG-characteristic domains) and whether orthology to K63-chain-forming RGLG enzymes supports the K63-linkage-specific refinement, or whether the linkage specificity cannot be determined from sequence. ## Term and Decision Context - Term: protein K63-linked ubiquitination (GO:0070534) ## Reference Context No specific reference context supplied. ## Source Context YAML ```yaml hypothesis: ProtNLM2 predicts that the Oryza sativa (japonica) protein Q6YYC5 catalyzes protein K63-linked ubiquitination (GO:0070534), a linkage-specific refinement of its existing generic GO:0016567 (protein ubiquitination) annotation. Its Arabidopsis ortholog RGLG2 (a RING-domain E3 ligase) assembles K63-linked polyubiquitin chains. Independently assess whether Q6YYC5 has the domain architecture of a functional RGLG-family E3 ubiquitin ligase (a catalytic RING-type zinc-finger domain, plus any vWA or other RGLG-characteristic domains) and whether orthology to K63-chain-forming RGLG enzymes supports the K63-linkage-specific refinement, or whether the linkage specificity cannot be determined from sequence. focus_type: computational_prediction term_id: GO:0070534 term_label: protein K63-linked ubiquitination context: [] reference_id: [] ``` ## Research Objective Build a focused report that helps a curator decide whether this hypothesis should affect the gene review. Address the focus type directly: 1. For an existing GO annotation decision, evaluate whether the current action is justified, too strong, too weak, or should change. 2. For a proposed replacement or new GO term, evaluate whether the term is biologically supported, too broad, too narrow, or missing key qualifiers. 3. For a computational prediction, evaluate whether the prediction is correct, less precise than existing knowledge, uncertain, or likely wrong because of paralog overannotation, frequency bias, pathway context, or in vitro-only activity. 4. For a core-function hypothesis, evaluate whether the proposed activity, process, and location represent the gene product's primary function rather than a downstream effect, pleiotropic phenotype, or context-specific role. 5. For a function-assignment hypothesis, evaluate whether the gene product directly has the stated GO term/function. Treat the prior review action, if any, as intentionally blinded unless it appears in the supplied context. Use primary literature whenever possible. Prefer PMID citations and include DOI citations when no PMID is available. Treat reviews and database records as orientation unless they contain directly relevant synthesized evidence that is clearly labeled as review-level or database-level support. Evaluate the hypothesis from the supplied seed context, primary literature, and publicly accessible bioinformatics resources. Local `*-bioinformatics` analyses, when they already exist in the repository, are intentionally withheld from this prompt so the report can be compared against them after the run. Do not rely on literature alone. Where the hypothesis is decidable by computation, actually run the analysis and keep it as provenance rather than only reasoning about it. Match the analysis to the question, for example: - membrane topology / localization: compute a hydropathy profile and predicted transmembrane segments from the sequence, and locate signal peptides and targeting/sorting motifs (e.g. dileucine, acidic-cluster, NLS); compare against UniProt topology features and AlphaFold geometry. - catalytic / binding activity: check whether the specific active-site, metal-binding, or motif residues are present and correctly spaced (in sequence and, where useful, structure) and compare to characterized family members. - DNA-binding / regulatory: examine the binding-domain class, obligate partners, and known binding-motif / PWM signatures. - family / paralog questions: use domain (Pfam/InterPro), orthology, and conservation comparisons to distinguish subfamilies. Use resources you can actually access programmatically (UniProt, AlphaFold DB, InterPro, sequence computation, public APIs). If a resource is web-only or you cannot run a check, say so plainly instead of guessing — never fabricate a result, and an inconclusive or "could not run" analysis is an acceptable and useful outcome. Report all computational results conservatively and prefer recording the underlying analysis (code, computed values, table, or plot) as provenance. ## Required Output ### Executive Judgment Give a concise verdict: supported, partially supported, unresolved, weakly supported, over-annotated, or refuted. Explain the reasoning and the most important caveats. ### Evidence Matrix Create a table with one row per important evidence item: - Citation (PMID preferred) - Evidence type (direct assay, mutant phenotype, localization, interaction, structural/evolutionary, computational, review/database) - Supports / refutes / qualifies / competing - Claim tested - Key finding - Organism, tissue, cell type, or assay context - Confidence and limitations ### GO Curation Implications State the likely curation action as a lead requiring curator verification. If GO terms are involved, explain whether the evidence supports an MF, BP, or CC term, and whether the term should be retained, removed, generalized, made more specific, or treated as non-core. Avoid using "protein binding" as a final recommendation unless no more informative term is supported. ### Mechanistic Scope Describe the immediate molecular or cellular function being tested. Separate direct gene-product activity from downstream phenotypes, pathway consequences, developmental outcomes, disease manifestations, or effects inferred only from loss of function. ### Conflicts and Alternatives Identify evidence that conflicts with the seed hypothesis or suggests an alternative interpretation, including paralog confusion, organism-specific differences, isoform-specific findings, experimental artifacts, or database carry-over. ### Knowledge Gaps List explicit uncertainties that matter for curation. For each gap, state what was checked, why the gap matters, and what evidence or experiment would resolve it. ### Discriminating Tests Recommend concrete assays, perturbations, datasets, or comparative analyses that would most efficiently distinguish this hypothesis from alternatives. ### Curation Leads Provide candidate updates for the review, clearly labeled as leads requiring curator verification. Include candidate references with exact snippets to verify, candidate replacement or new GO terms, possible action changes, suggested questions, and suggested experiments. If the provider supports artifacts, save provenance for any analysis you run — the executed code together with its output (computed values, plot, or table), not just a summary figure — alongside artifact-friendly tables such as an evidence matrix, GO decision table, or comparison table. Genuine computed provenance is more valuable than a hand-drawn summary, and you must not synthesize a figure that implies an analysis you did not actually run. These artifacts are important provenance for hypothesis-level review. ## Output # Hypothesis Review: Q6YYC5 (*Oryza sativa* japonica, Os08g0135400) — protein K63-linked ubiquitination (GO:0070534) **Focus type:** computational_prediction (ProtNLM2) — proposed linkage-specific refinement of GO:0016567 → GO:0070534 **Term under evaluation:** protein K63-linked ubiquitination (GO:0070534) **Investigation:** 3 iterations · 5 confirmed findings · 12 papers reviewed --- ## Summary Q6YYC5 is a genuine member of the RGLG (RING Domain Ligase) family of E3 ubiquitin ligases. Independent domain analysis confirms it carries the two hallmark features of the family: an N-terminal von Willebrand factor type A (vWA) domain and a C-terminal, **intact** C3HC4 RING-type zinc finger with all eight canonical metal-coordinating residues present and correctly spaced. This architecture firmly justifies the protein's **generic** annotations for protein ubiquitination (GO:0016567) and ubiquitin–protein transferase activity (GO:0004842). Its identity as a functional E3 ligase is not in doubt. The ProtNLM2 refinement to **protein K63-linked ubiquitination (GO:0070534)** is, however, an **over-annotation** that should not be propagated. The prediction fails on two independent grounds. First and most decisively, ubiquitin-chain linkage in RING-type E3 ligases is determined by the cognate E2-conjugating enzyme, not by the E3's own sequence — the same RING E3 can build K63 chains with one E2 and K48 chains with another, so linkage specificity cannot be read out from an E3 sequence. Second, the orthology argument used to justify the refinement is misdirected: K63-chain assembly was demonstrated in vitro only for *Arabidopsis* RGLG2 (and inferred for its closest sequelog RGLG1), but Q6YYC5 is phylogenetically closest to the **RGLG3/RGLG4** clade (~60% identity to RGLG4). That clade uses a different E2 (UBC30) and drives **degradative** ubiquitination of its substrate GRXS17 — the opposite of an obligate K63-signaling signature. **Bottom line for curators:** Retain the generic ubiquitination/E3-ligase terms (well supported by structure and family membership). Do **not** add GO:0070534 to Q6YYC5. The linkage specialization is not decidable from sequence or orthology and would require a direct in vitro chain-linkage assay with the rice cognate E2 to establish. Verdict: **generic function supported; K63 refinement over-annotated / weakly supported.** --- ## Key Findings ### F001 — Q6YYC5 has canonical RGLG-family architecture (vWA + intact C3HC4 RING) UniProt Q6YYC5 (gene Os08g0135400; 401 amino acids) carries the two defining domains of the RGLG family. InterPro, Pfam, and SMART annotate an N-terminal **von Willebrand factor type A (vWA) domain** (IPR002035; SMART SM00327) together with a C-terminal **RING-type zinc finger** at residues 356–389 (Pfam PF13920, zf-C3HC4_3; PROSITE PS50089). Critically, the catalytic RING is intact rather than degenerate: the computed C3HC4 cross-brace contains all eight metal-coordinating ligands in canonical spacing — C356, C359, C370, H372, C374/375, C378, C385, and C388 — and the sequence matches the canonical C3HC4 RING regular expression (`C..C.{9,39}C.{1,3}H.{2,3}C..C.{4,48}C..C`). PANTHER independently classifies the protein under subfamily **PTHR45751:SF16 "E3 UBIQUITIN-PROTEIN LIGASE RGLG4."** The combination of an N-terminal vWA domain and a C-terminal foldable catalytic RING is the RGLG-family signature. This finding establishes Q6YYC5 as a bona fide E3 ubiquitin ligase and justifies the generic ubiquitination annotations — but says nothing about chain linkage. ### F002 — Q6YYC5 is closest to *Arabidopsis* RGLG4/RGLG3, not to the K63-demonstrated RGLG1/RGLG2 Global pairwise alignment of Q6YYC5 against the five reviewed *Arabidopsis* RGLG proteins yields the following percent identities: **RGLG4 59.8%**, RGLG5 56.6%, RGLG3 56.1%, RGLG2 52.8%, and RGLG1 48.5%. The closest paralog, RGLG4, is also identical in length (401 aa) to Q6YYC5, consistent with the independent PANTHER subfamily assignment (SF16 = RGLG4). This distinction is the crux of the review, because the K63-chain-forming activity that motivates the hypothesis was demonstrated **in vitro only for RGLG2** (and inferred for RGLG1) in [PMID: 17586653](https://pubmed.ncbi.nlm.nih.gov/17586653/). Q6YYC5's own clade (RGLG3/RGLG4) has a distinct, characterized biochemistry: it partners with the cognate E2 **UBC30** and drives degradation of the substrate GRXS17 ([PMID: 27497447](https://pubmed.ncbi.nlm.nih.gov/27497447/)) — a degradative outcome that runs counter to the non-degradative signaling role classically ascribed to K63 chains. The orthology bridge required to transfer "K63" from RGLG2 to Q6YYC5 therefore does not hold; Q6YYC5 sits in the wrong sub-branch of the family. ### F003 — Ubiquitin-chain linkage specificity of RING E3s is set by the E2 partner, not by the E3 sequence This is the central mechanistic reason the K63 refinement is not sequence-decidable. RING-type E3s do not form a catalytic thioester intermediate; they transfer ubiquitin **directly** from the E2~Ub conjugate to the substrate, so the geometry that determines which lysine of the acceptor ubiquitin is attacked — and hence the chain linkage — is contributed by the E2. As stated verbatim in [PMID: 40169231](https://pubmed.ncbi.nlm.nih.gov/40169231/): *"RING-type E3s mediate the transfer of Ub directly from the E2∼Ub conjugate, implying that the specificity of Ub linkage is determined by the given E2."* This is not merely a theoretical concern: [PMID: 17426036](https://pubmed.ncbi.nlm.nih.gov/17426036/) shows experimentally that a single RING E3 (MuRF1) builds **K63 chains with the E2 UbcH13/Uev1a but K48 chains with the E2 UbcH1 (E2-25K)**. Because Q6YYC5's cognate rice E2 is unknown and no linkage assay has been performed on the rice protein, the chain type it would produce cannot be inferred from its own sequence. A RING E3 is, on its own, linkage-agnostic. ### F004 — Neighbor-joining tree confirms Q6YYC5 is sister to RGLG4, separate from the K63-forming RGLG1/RGLG2 clade An independent phylogenetic reconstruction reinforces F002. A neighbor-joining tree built from a six-sequence global-alignment distance matrix produced the following topology (Newick): ``` ((RGLG3:23.7,(RGLG5:17.7,(RGLG1:16.3,RGLG2:12.4):7.1):6.9):0.6,(Q6YYC5_Os:18.9,RGLG4:21.4):0.6); ``` Q6YYC5 pairs with RGLG4 as a sister leaf, while **RGLG1 and RGLG2 — the K63-demonstrated ligases — form their own tight clade** (pairwise distance 28.6 between them, versus Q6YYC5's much larger distances of ~40–52 to that pair). Additionally, Q6YYC5 retains an N-terminal Gly2 (sequence begins "MGG…"), a potential N-myristoylation site analogous to the one that targets RGLG2 to the plasma membrane. This retained motif is a conserved family feature but does not bear on linkage specificity. The tree topology cleanly separates Q6YYC5 from the K63-forming branch, corroborating the identity-based clade assignment. ### F005 — K63-chain formation in the RGLG pathway requires the K63-specific E2 UBC13, whose cognate E3s are RGLG1/RGLG2 (not the RGLG4 clade) The genetic and biochemical partitioning of the RGLG family is explicit in the literature. [PMID: 20113438](https://pubmed.ncbi.nlm.nih.gov/20113438/) (Li & Schmidt, 2010) reports that UBC13 *"has been shown to catalyze non-canonical Lys63-linked ubiquitin chains,"* and that *"Mutations in the cognate E3 ligases RGLG2 and RGLG1 caused the constitutive formation of branched root hairs,"* tying the K63/UBC13 activity specifically to RGLG1/RGLG2 in the iron-deficiency response. In direct contrast, the RGLG3/RGLG4 clade — the clade to which Q6YYC5 belongs — uses the E2 UBC30 to drive GRXS17 degradation ([PMID: 27497447](https://pubmed.ncbi.nlm.nih.gov/27497447/)). No published evidence links Q6YYC5, or the RGLG4 clade more broadly, to UBC13 or to K63 chains. The K63 module is therefore an RGLG1/RGLG2 + UBC13 property, and there is no basis to extend it to Q6YYC5. --- ## Mechanistic Model / Interpretation The seed hypothesis can be laid out as a three-link inference chain, and this investigation shows precisely where each link holds or fails: ``` Link 1: Q6YYC5 is an RGLG-family RING E3 ligase → HOLDS (F001, F004) Link 2: RGLG-family E3s form K63 chains → PARTIAL (only RGLG1/2, via E2 UBC13) Link 3: Therefore Q6YYC5 forms K63 chains → FAILS (F002, F003, F005) ``` The failure is best understood through how RING E3 catalysis actually works. The RING E3 is a scaffold that juxtaposes the charged E2~Ub conjugate and the substrate; it does not itself select the acceptor lysine: ``` E2~Ub ──────► substrate–Ub ──────► poly-Ub chain │ │ (chain linkage type The RING E3 (Q6YYC5) positions E2~Ub is set HERE, by the E2) and substrate. It does NOT dictate K48 vs K63 on its own. ``` Within the *Arabidopsis* RGLG family there are two functionally distinct modules, and Q6YYC5 maps onto the non-K63 one: | Sub-branch | Members | Cognate E2 | Chain / outcome | Characterized biology | |---|---|---|---|---| | RGLG1/RGLG2 | RGLG1, RGLG2 | **UBC13** | **K63**, non-degradative signaling | Apical dominance, auxin transport (PIN), Fe-deficiency root-hair branching | | RGLG3/RGLG4 | RGLG3, RGLG4 | **UBC30** | degradative | GRXS17 degradation; jasmonate signaling; FB1-triggered PCD | Q6YYC5 maps by both sequence identity (F002) and tree topology (F004) onto the **RGLG3/RGLG4** row — the row associated with UBC30 and degradative ubiquitination, not with UBC13 and K63. Even granting for argument's sake that any RGLG could build K63 chains given the right E2, that E2 (UBC13) and its cognate-E3 pairing are documented specifically for RGLG1/RGLG2. Q6YYC5's cognate rice E2 has never been identified, and no chain-linkage assay has been performed on the rice protein. The practical consequence for GO curation is that the generic term "protein ubiquitination" captures everything the sequence and orthology can support, whereas the linkage-specific "K63-linked ubiquitination" term asserts a mechanistic property (E2-dependent linkage geometry) that the E3 sequence cannot encode. ProtNLM2's refinement is a plausible-sounding but mechanistically unfounded increase in specificity — a textbook case of a language-model annotation being **more precise than the underlying evidence permits**, likely driven by paralog frequency bias (transfer of the well-published RGLG2 K63 result onto a more distant relative). --- ## Evidence Base / Evidence Matrix | Citation | Evidence type | Supports/Refutes/Qualifies | Claim tested | Key finding | Context | Confidence / limitations | |---|---|---|---|---|---|---| | UniProt Q6YYC5 + InterPro/Pfam/PANTHER (database) | Structural/evolutionary; computational | Supports (generic); Qualifies (K63) | Does Q6YYC5 have RGLG E3 architecture? | vWA (IPR002035) + C-terminal C3HC4 RING (PF13920, res 356–389); PANTHER SF16 = RGLG4 | Rice protein, 401 aa | High for architecture; database-level | | This work (computed) | Computational (motif) | Supports (E3 activity) | Is the catalytic RING intact? | Canonical C3HC4 cross-brace present: C356,C359,C370,H372,C374/5,C378,C385,C388; regex match | Sequence analysis | High; predicts catalytic competence, not linkage | | This work (computed) | Structural/evolutionary | Refutes (K63 orthology) | Which At RGLG is Q6YYC5 closest to? | RGLG4 59.8% > RGLG5 56.6 > RGLG3 56.1 > RGLG2 52.8 > RGLG1 48.5%; NJ tree: Q6YYC5 sister to RGLG4; RGLG1+RGLG2 separate clade | Global alignment + NJ, 6 seqs | Medium-high; family-level, not strict 1:1 orthology | | [PMID: 17586653](https://pubmed.ncbi.nlm.nih.gov/17586653/) | Direct assay + mutant phenotype | Qualifies | Do RGLGs form K63 chains? | RGLG2 forms K63-linked multiubiquitin chains in vitro; rglg1 rglg2 loses apical dominance (auxin/PIN) | Arabidopsis; in vitro + genetics | High for RGLG1/2; not Q6YYC5's clade | | [PMID: 27497447](https://pubmed.ncbi.nlm.nih.gov/27497447/) | Direct assay + interaction | Refutes (K63 for RGLG3/4 clade) | What do RGLG3/RGLG4 do? | RGLG3/4 + cognate E2 UBC30 ubiquitinate GRXS17 → degradation | Arabidopsis; TAP + in vitro | High; degradative outcome argues against K63 for the RGLG4 clade | | [PMID: 40169231](https://pubmed.ncbi.nlm.nih.gov/40169231/) | Mechanistic/structural | Refutes (sequence-decidability) | Is linkage set by E3 or E2? | "specificity of Ub linkage is determined by the given E2" for RING E3s | Listerin RQC system | High; general RING principle | | [PMID: 17426036](https://pubmed.ncbi.nlm.nih.gov/17426036/) | Direct assay | Refutes (sequence-decidability) | Can one RING make different linkages? | MuRF1 makes K63 with UbcH13/Uev1a but K48 with E2-25K | In vitro reconstitution | High; direct demonstration | | [PMID: 20113438](https://pubmed.ncbi.nlm.nih.gov/20113438/) | Direct assay + genetics | Refutes (K63 for Q6YYC5) | Which E2/E3 make K63 in RGLG pathway? | UBC13 (K63-specific E2) has cognate E3s RGLG1/RGLG2 (Fe-deficiency root hairs) | Arabidopsis/cucumber | High; ties K63 to RGLG1/2+UBC13, not RGLG4 clade | | [PMID: 40451499](https://pubmed.ncbi.nlm.nih.gov/40451499/) | Direct assay + structural | Refutes (sequence-decidability) | Does one E3 use multiple E2s/linkages? | Arkadia/Ark2C functionally interact with several E2s (incl. Ubc13) to build different chains | In vitro | High; reinforces E2-dependence | | [PMID: 23625358](https://pubmed.ncbi.nlm.nih.gov/23625358/) | Mutant phenotype | Qualifies | RGLG1/2 substrates | rglg1 rglg2 stabilizes AtERF53 (RGLG1/2 promote its turnover) | Arabidopsis | Medium; RGLG1/2-specific | | [PMID: 22898498](https://pubmed.ncbi.nlm.nih.gov/22898498/) / [PMID: 23073017](https://pubmed.ncbi.nlm.nih.gov/23073017/) / [PMID: 25788731](https://pubmed.ncbi.nlm.nih.gov/25788731/) | Mutant phenotype | Qualifies | RGLG3/4 biological role | RGLG3/4 modulate COI1-dependent jasmonate signaling & FB1-triggered PCD | Arabidopsis genetics | Medium; process context for the clade | | [PMID: 41312104](https://pubmed.ncbi.nlm.nih.gov/41312104/) | Direct assay | Qualifies (competing linkage) | Rice RGLG chain type | OsRGLG6 ubiquitinates OsOTUB1 for degradation (grain number/yield) | Rice | Medium; different rice RGLG, degradative activity | --- ## GO Curation Implications Leads requiring curator verification: - **GO:0004842 (MF, ubiquitin-protein transferase activity)** — **RETAIN.** Supported by intact RING + vWA architecture (F001). - **GO:0016567 (BP, protein ubiquitination)** — **RETAIN** as the appropriately general term. - **GO:0070534 (BP, protein K63-linked ubiquitination)** — **DO NOT ADD** on the basis of the ProtNLM2 prediction. It over-specifies a property (chain linkage) that is E2-determined and not encoded in the E3 sequence (F003); the orthology used to justify it points to RGLG4, the degradative clade (F002, F004), not the K63-demonstrated RGLG1/2 (F005). Treat as an over-annotation / paralog-frequency-bias artifact. - **Localization (CC):** Q6YYC5 begins "MGG…" (Gly2), a potential N-myristoylation site as in plasma-membrane–localized RGLG2. This is a lead for a membrane-localization annotation but must be verified independently before use. The correct curation posture is to keep the annotation at the **generic granularity** the evidence supports and to flag GO:0070534 as an example of computational over-specification. --- ## Mechanistic Scope The immediate molecular function under test is **E3 ubiquitin-ligase activity** — Q6YYC5 acting as a RING-type scaffold that positions an E2~Ub conjugate and a substrate to transfer ubiquitin. That direct activity is well supported. The **K63 linkage** is a downstream property of the E2 partner and the reaction context, not an intrinsic property of Q6YYC5. The seed hypothesis conflates three distinct levels: - **Direct gene-product activity:** RING-dependent ubiquitin transfer (supported). - **E2-contributed reaction property:** chain linkage type (K48/K63/mixed) — belongs to the E2, not the E3 (not supported for K63 here). - **Downstream/phenotypic outcomes** in relatives: apical dominance, auxin transport, jasmonate signaling, Fe-deficiency root-hair branching, GRXS17 degradation — pathway consequences of specific RGLG members, not evidence that Q6YYC5 itself builds K63 chains. Curators should record only the direct activity at the granularity the evidence permits. --- ## Conflicts and Alternatives - **Paralog confusion (primary risk):** ProtNLM2 likely transferred the well-published K63 result from RGLG1/RGLG2, but Q6YYC5 clusters with RGLG4. The RGLG3/4 clade drives substrate **degradation** via UBC30 — inconsistent with obligate K63 (which is typically non-degradative/signaling). - **Organism difference:** Rice has its own RGLG expansion; the closest *Arabidopsis* match (RGLG4, 59.8%) is a paralog-level, not strict-ortholog, relationship, weakening any functional transfer. The one characterized rice RGLG (OsRGLG6, [PMID: 41312104](https://pubmed.ncbi.nlm.nih.gov/41312104/)) is degradative, again pointing away from a K63-signaling default. - **In-vitro-only caveat:** Even the RGLG2 K63 result is an in vitro chain-formation assay with a chosen E2; it does not license a rice-protein-specific K63 term. - **Database carry-over risk:** ProtNLM2 is a language-model annotator prone to propagating specific-sounding terms; GO:0070534 here appears to be exactly such an over-specification. --- ## Limitations and Knowledge Gaps 1. **Cognate E2 of Q6YYC5 (unknown).** Checked: no interaction data found. Matters because the E2 sets linkage. Resolve: yeast-two-hybrid / AlphaFold-Multimer E2-panel screen; test K63-specific (OsUBC13/UEV) vs promiscuous vs UBC30-type E2s. 2. **Actual chain product (unknown).** Checked: no biochemical assay exists for Q6YYC5. Resolve: in vitro ubiquitination with ubiquitin lysine-only mutants (K63-only, K48-only, K0) + LC-MS/MS linkage typing. 3. **True rice ortholog assignment.** Checked family identity and a 6-sequence NJ tree only. Resolve: bootstrapped phylogeny of all rice + *Arabidopsis* RGLGs; syntenic ortholog call. 4. **Substrate and degradative vs signaling role.** Resolve: RING-dead substrate-trap TAP-MS in rice. 5. **Membrane localization not experimentally verified.** The Gly2 myristoylation motif is a prediction only. Resolve: subcellular localization of tagged Q6YYC5. Methodological limitation: pairwise identities were computed with a simple global alignment (match/mismatch scoring), adequate for ranking paralogs but not a substitute for a bootstrapped phylogeny. Domain calls are database-derived (InterPro/Pfam/PANTHER). No experimental data specific to Q6YYC5 were located; conclusions about the K63 term rest on the general RING mechanism plus clade assignment. --- ## Proposed Follow-up Experiments / Discriminating Tests 1. **In vitro ubiquitination with ubiquitin lysine mutants** (K63-only vs K48-only vs K0) + LC-MS/MS linkage typing — directly reads out the chain linkage Q6YYC5 produces. *Most decisive test.* 2. **E2 pairing screen** — determine whether Q6YYC5 productively pairs with a K63-specific UBC13/UEV1 dimer, or with a UBC30-type E2 (predicting degradation). 3. **Substrate stability assays** — if candidate substrates are stabilized in a Q6YYC5 mutant (degradation phenotype), K63 is less likely; if a signaling readout changes without degradation, K63 is more consistent. 4. **Cross-species complementation** — test whether Q6YYC5 rescues *Arabidopsis* rglg3 rglg4 (jasmonate/GRXS17 phenotypes) versus rglg1 rglg2 (apical dominance) to assign functional clade. 5. **Phylogenomic tree** of all rice + *Arabidopsis* RGLGs with bootstrap support to confirm the RGLG3/4 vs RGLG1/2 clade placement. 6. **AlphaFold RING/vWA structural superposition** onto characterized RGLG2 and RGLG4 to confirm catalytic geometry. --- ## Curation Leads (require curator verification) - **Action:** Keep GO:0016567 / GO:0004842; **reject the ProtNLM2 GO:0070534 addition** as over-specific / computational-only. - **Candidate reference + snippet (E2 determines linkage):** [PMID: 40169231](https://pubmed.ncbi.nlm.nih.gov/40169231/) — *"RING-type E3s mediate the transfer of Ub directly from the E2∼Ub conjugate, implying that the specificity of Ub linkage is determined by the given E2."* - **Candidate reference + snippet (only RGLG2 shown to form K63):** [PMID: 17586653](https://pubmed.ncbi.nlm.nih.gov/17586653/) — *"The RING domain protein RGLG2 … can form Lys-63-linked multiubiquitin chains in an in vitro reaction."* - **Candidate reference + snippet (K63 module = RGLG1/2 + UBC13):** [PMID: 20113438](https://pubmed.ncbi.nlm.nih.gov/20113438/) — *"UBC13 has been shown to catalyze non-canonical Lys63-linked ubiquitin chains … Mutations in the cognate E3 ligases RGLG2 and RGLG1 caused the constitutive formation of branched root hairs."* - **Candidate reference + snippet (Q6YYC5 clade = degradative, UBC30):** [PMID: 27497447](https://pubmed.ncbi.nlm.nih.gov/27497447/) — *"we used a ubiquitin-conjugating enzyme (UBC) panel screen to pinpoint UBC30 as a cognate E2 UBC … mediating … ubiquitination of GRXS17 … GRXS17 is ubiquitinated and degraded in an RGLG3- and RGLG4-dependent manner."* - **Suggested question for curators:** Is there any rice-specific biochemical evidence (E2 partner or chain-type assay) for Q6YYC5? If not, the linkage-specific term should not be propagated. - **Suggested experiment:** In vitro linkage-typing assay (above) to decide GO:0070534 vs generic GO:0016567. --- ## Provenance Artifacts Computed provenance saved under `artifacts/`: - `Q6YYC5_RGLG_distance_matrix.csv` — pairwise distances (100 − %id) + Newick NJ tree. - `Q6YYC5_evidence_matrix.csv` — machine-readable evidence table. - `Q6YYC5_GO_decision_table.csv` — GO curation recommendations. --- ## Conclusion Q6YYC5 is a bona fide RGLG-family RING E3 ubiquitin ligase — it carries the diagnostic vWA domain plus an intact C3HC4 RING (catalytic ligands C356/C359/C370/H372/C374-5/C378/C385/C388) — so its generic annotations GO:0016567 (protein ubiquitination) and GO:0004842 (ubiquitin-protein transferase activity) are well justified. The ProtNLM2 refinement to protein K63-linked ubiquitination (GO:0070534) is **over-annotated** and should not be added: ubiquitin-chain linkage in RING E3s is determined by the cognate E2, not by the E3 sequence, and Q6YYC5's closest *Arabidopsis* relatives are the RGLG3/RGLG4 clade (RGLG4 ~60% identity), which uses E2 UBC30 to drive degradation, rather than the K63-chain-forming RGLG1/RGLG2. No rice-specific E2 or chain-type assay exists, so the K63 term is not decidable from sequence/orthology and requires direct biochemical verification. ## Artifacts - [OpenScientist Q6YYC5 GO decision table](openscientist_artifacts/artifacts_Q6YYC5_GO_decision_table.csv) - [OpenScientist Q6YYC5 RGLG distance matrix](openscientist_artifacts/artifacts_Q6YYC5_RGLG_distance_matrix.csv) - [OpenScientist Q6YYC5 evidence matrix](openscientist_artifacts/artifacts_Q6YYC5_evidence_matrix.csv) - [OpenScientist final report](openscientist_artifacts/final_report.html) - [OpenScientist final report](openscientist_artifacts/final_report.pdf)