The InterPro2GO mapping assigns YET2 the BAP29/BAP31 signatures (IPR008417, IPR040463; Pfam PF05529) and the GO terms attached to them - endoplasmic reticulum, membrane, and intracellular protein transport. These are family-level consequences of the domain match, so the two localization terms are well founded while the transport term inherits a mammalian BAP31 role never demonstrated for Yet2p.

SGD assigned the root terms GO:0003674 and GO:0008150 to YET2 with the ND evidence code, formally recording that no experimental data establish either a molecular function or a biological process for Yet2p. The ER localization is the only aspect with direct observational support.

PAINT placed Yet2p inside the BAP29/BAP31 clade (PANTHER PTHR12701, PTN000294723), propagating the ER membrane location together with mammalian BAP31 process terms (ER-to-cytosol retrograde transport, positive regulation of ubiquitin-dependent catabolism) and, in the current local PAINT cache, protein translocation chaperone activity. The location is corroborated independently by topology, the C-terminal di-lysine motif and direct imaging; the process and molecular-function terms rest on the mammalian descendant, with no yeast experiment supporting them for Yet2p.

The ER membrane annotation from this source is a vocabulary mapping of the UniProt SUBCELLULAR LOCATION line "Endoplasmic reticulum membrane; Multi-pass membrane protein", which UniProt itself tags ECO:0000250 (by similarity) rather than as a direct observation on Yet2p.

Yet2p was localized to the ER as part of a systematic N-terminal GFP-tagged library of ~1,800 endomembrane proteins. This is the source of the HDA C:endoplasmic reticulum annotation (ECO:0007005): a genuine direct observation, but a high-throughput one, and not a functional characterization of the gene.

Human BCAP31, the experimental descendant seeding the two ERAD-related IBDs at PANTHER:PTN000294723, associates with Sec61/Derlin-1 and promotes CFTRDeltaF508 retrotranslocation and proteasomal degradation.

The stable unit of the yeast BAP31 family is a Yet1p-Yet3p heterocomplex whose assembly is needed for subunit stability and correct ER localization. Yet2p is not reported as a member of this complex, which is the basis for treating its partners as unknown rather than assuming paralog redundancy.

The Yet complex is not packaged into COPII vesicles and so does not act as an ER export receptor; instead a fraction associates with the Sec translocation apparatus, and that association increases under ER stress. This argues against transplanting the mammalian BAP31 "ER export receptor" role onto the yeast family, including Yet2p.

The Wilson and Barlowe full text explains why Yet2p should not simply be folded into the constitutive Yet1p-Yet3p complex; Yet2p-MYC has only minor co-association with Yet1p and the Sec complex, and is dispensable for Yet3p-HA co-immunoprecipitation of Yet1p and Sec-complex components.

Deleting YET2 did not perturb the core Yet1p-Yet3p/Sec association, further supporting the interpretation that Yet2p is not a stable subunit of the characterized Yet complex.

The inositol-starvation growth defect is reported for yet1 and yet3 deletions specifically; no such requirement is attributed to YET2 anywhere in the abstract, so inositol prototrophy is a paralog phenotype and not a YET2 annotation basis.

Yet2p-MYC is strongly induced by DTT-induced ER stress, establishing a tested stimulus for its otherwise non-constitutive expression.

The yet1 yet2 yet3 triple mutant was fully competent for CPY and alpha-factor translocation, arguing that the Yet proteins are not generally required for translocation of the two tested substrates.

Wilson and Barlowe did not detect broad ER-stress or ERAD defects in yet mutants; the triple mutant grew on DTT/tunicamycin, CPY* and Ste6* turnover were unaffected in the triple mutant, and prior work had found a wild-type CPY* degradation rate in yet2Δ.

Zung et al. directly compared the endogenous levels of C-terminally GFP-tagged Yet1p, Yet2p and Yet3p and found that Yet3p is more abundant than either paralog; their paper focuses on Yet3p, but its direct YET2 observation helps distinguish low-abundance Yet2p from the constitutive Yet1p-Yet3p branch.

The authors explicitly frame YET2 as potentially functionally distinct from YET1 and YET3, reinforcing the decision not to transfer Yet3-specific sterol-contact-site biology into YET2 core functions.

UniProt's only FUNCTION statement for Yet2p is hedged ("May play a role") and is sourced to the non-PubMed-indexed Toikkanen et al. 2006 reference, so it does not constitute evidence sufficient to annotate a molecular function or a transport process.

Yet2p is a 160-residue multi-pass ER membrane protein with three transmembrane helices (3-23, 46-66, 104-124), a lumenal N-terminus and a cytoplasmic C-terminal tail (125-160) - the canonical BAP31-type architecture.

A di-lysine motif at residues 157-160 in the cytoplasmic tail provides the ER-retrieval signal underpinning steady-state ER residence.

Yet2p belongs to the BCAP29/BCAP31 family (Pfam PF05529 Bap31; InterPro IPR008417, IPR040463; PANTHER PTHR12701), the family shared with Yet1p, Yet3p and mammalian BAP29/BAP31.

Yet2p is a low-abundance, non-constitutively expressed yeast BAP31-family paralog. The observation (from Zung et al. 2024) that Yet2p differs in this way from Yet1p and Yet3p argues it is not simply redundant with the Yet1p-Yet3p branch and is instead conditionally regulated. The inducing conditions are not established.

The report finds essentially no YET2-specific primary literature: the gene is characterized almost entirely through its better-studied paralogs, so the family-level material it summarizes (Yet3 ergosterol/ERGosome scaffolding, Yet1p-Yet3p Opi1/inositol regulation, mammalian BAP31 sorting) is paralog context rather than YET2 evidence.