Q8MST5 is the selected 457-residue betaTub97EF sequence with tubulin GTPase and C-terminal tubulin domains. PMID:29084803(https://pubmed.ncbi.nlm.nih.gov/29084803/), DOI https://doi.org/10.1242/dev.156109, directly establishes target-dependent microtubule stabilization in hemocytes and gut and increased expression at 14°C. It supports the broad structural/process predictions independently of electronic annotations. The accessible standard cache is abstract-only, so detailed isoform-specific kinetics and a dedicated mitotic requirement are not claimed.
PMID:9428769(https://pubmed.ncbi.nlm.nih.gov/9428769/) and PMID:9628483(https://pubmed.ncbi.nlm.nih.gov/9628483/) provide experimental structural grounding for conserved tubulin GTP binding and hydrolysis. This is justified transfer of core tubulin chemistry; alpha-subunit nonexchangeable GTP and beta-subunit exchangeable GTP are not conflated. Fifteen GOA rows are reviewed, and the ProtNLM process is LSP relative to supported microtubule cytoskeleton organization.
The selected frozen UniProt record is retained in betaTub97EF-uniprot-source.json, with the complete original prediction metadata in betaTub97EF-predictions-source.json. It maps the exact accession to this FlyBase gene; current sequence identity does not establish the historical predictor input. Gene-level experiments support conserved functions unless a relevant isoform difference is established. Falcon research was requested with perplexity-lite fallback alongside publication caching. Primary publications and sequence observations, rather than AI summaries or ARBA assertions, support the curated conclusions.
The publisher full text was inspected, and selected primary excerpts record spindle staining and isoform caveats. Both exon-4B and exon-4C forms partially rescue betaTub56D loss; the main text states that “UASt-βTub97EF(4B) and UASt-βTub97EF(4C) provided only limited rescue.” The specific stability experiments use 4B, and cold induction differs between 4B and 4C. Sequence comparison establishes Q8MST5 equals RefSeq variant B, but does not equate that transcript label with exon4B. Main biological text therefore separates the major4B cold response from the selected sequence’s generic tubulin role. The mitotic IBA is retained as noncore based on direct spindle localization. The standard cache remains abstract-only; full publisher text and the accessible supplement were inspected through web access.
The completed Falcon report was read in full after the wrapper timeout; the original child returned a complete report. Its primary-paper synthesis agrees with the independently inspected publisher text: both 4B and 4C forms support a broad microtubule role, whereas the detailed stabilization experiments and cold induction concern the predominant 4B form. The report does not map Q8MST5 to the paper’s exon names, so that exact correspondence remains explicitly unresolved. Generic tubulin GTP chemistry is retained as supported family inference; a structural role does not mean the beta-tubulin subunit lacks GTPase activity. Proposed upstream temperature-regulatory pathways are not assigned from a different gene’s enhancer experiments. No additional annotation change is required from the provider report.
ProtNLM2 output was not opened or used. Evidence: PMID:29084803 (abstract cache plus the existing publisher-text excerpts), the falcon deep-research report, PMID:9428769, PMID:9989499 (newly cached), PMID:9628483, and the PANTHER 19.0 tree.
Identity. Q8MST5 is an unreviewed TrEMBL entry (PE 2), 457 aa, full length with intact tubulin GTPase and C-terminal domains. It is not a fragment. It is one of two splice-isoform products of FBgn0003890: identical to E1JIZ8 and RefSeq NP_001163753.1 (transcript variant B), and differing from Q9VAX7 (also 457 aa) at 13 positions between residues 177 and 223, the mutually exclusive exon-4 region (RESULTS.md). Which accession is exon 4B and which is 4C is still not established. No reviewed (Swiss-Prot) canonical entry exists for this gene, so the same-gene-canonical relative rule does not apply.
Phylogenetic placement. PANTHER 19.0 puts Q8MST5 in PTHR11588:SF490 (TUBULIN BETA CHAIN), and it is the only member of that subfamily in the 20 reference proteomes. In the PANTHER tree its leaf node (PTN002266116) belongs to PTN008520933, together with an Anopheles and a Daphnia ortholog. That makes 97EF an arthropod-wide beta-tubulin lineage. PTN008520933 is sister (under PTN008974067, an arthropod node) to PTN000904125, which contains betaTub56D, betaTub60D and betaTub65B and their Anopheles/Tribolium/Daphnia counterparts. Both clades sit within PTN008520923, the metazoan beta-tubulin node that also holds human TUBB, TUBB1-TUBB8. Every IBA on this gene comes from the tubulin root node PTN000172598. No alpha- or gamma-specific IBD (e.g. gamma-tubulin complex, nucleator activity) is inherited, which is correct for a beta-tubulin. The PTHR11588 family review does not discuss subfamily placement of betaTub97EF, so there is nothing to disagree with. Its GO:0003924 scope is UNRESOLVED family-wide, and this gene-level review accepts the term only for the beta-tubulin E-site case (see below).
Changes from the previous review.
- GO:0005856 cytoskeleton (IEA) ACCEPT -> MODIFY to GO:0005874 microtubule. The term is correct but general, and the gene already carries the more specific term.
- GO:0007017 microtubule-based process (IEA) ACCEPT -> MODIFY to GO:0000226. Same reasoning.
- GO:0005737 cytoplasm (IBA) ACCEPT -> KEEP_AS_NON_CORE. This is the correct location of the soluble heterodimer pool. Microtubule is the core location.
- GO:0009653, GO:0048731, GO:0160108 (ARBA IEA) KEEP_AS_NON_CORE -> REMOVE. These are developmental-process predictions with no gene-specific support. Nulls are viable and fertile, with only a mild cold-specific embryonic survival defect and normal hindgut L/R asymmetry. Under the campaign rule, downstream organismal effects of microtubule stability are not process participation.
- GO:0003924 GTPase activity stays ACCEPT, with a corrected rationale. Beta-tubulin binds the exchangeable GTP (E site), and the proposed catalytic residue is supplied by alpha-tubulin of the adjacent dimer (PMID:9989499 "the proposed catalytic residue in alpha-tubulin is exposed at the minus end"). The hydrolytic site is therefore composite and active only in the polymer. Note that the UniProt CC FUNCTION line ("owing to GTPase activity of alpha-tubulin") is ARBA-derived, so it was not used as evidence either way.
- GO:0000278 mitotic cell cycle (IBA) stays KEEP_AS_NON_CORE. Spindle localization in wing discs is the evidence for it, but the gene is dispensable.
- Microtubule, structural constituent of cytoskeleton, GTP binding and microtubule cytoskeleton organization stay ACCEPT.
- Description rewritten. Core functions now include GTP binding. Added suggested questions (cold-response participation, exon-4B/4C accession mapping) and an in vitro dynamics experiment.
Not added. I did not propose a NEW term for cellular response to cold (GO:0070417). The cold induction is a property of the locus's regulation, and the protein's contribution is the same microtubule stabilization it provides at any temperature. This is raised as a suggested question.
Relative. No ortholog outside arthropods exists, and none of the arthropod orthologs is characterised. The nearest experimentally characterised relative is the sister-clade paralog betaTub56D (Q24560, PTHR11588:SF504), the major ubiquitous fly beta-tubulin used as the comparator in Myachina et al. 2017. The repo has no review for it. The repo has no module for microtubules or alpha/beta-tubulin. cct_chaperonin_folding.yaml treats tubulin only as a folding client.