## P4HB
- **UniProt:** P07237 · **batch:** proteostasis-batch-2026-06-07b · **review status:** COMPLETE
- **PN placement:** 2 rows — (1) `ER proteostasis|Folding enzyme|Protein disulfide isomerases`; (2) `ER proteostasis|Maturation and folding of specific substrates|ER collagen processing and folding`. **PN-node mapping:** PDI group=mapped→**GO:0003756 protein disulfide isomerase activity** (already_in_goa_exact); ER-collagen group=mapped→**GO:0032964 collagen biosynthetic process** (new_to_goa); classes/branch=no_mapping.
- **Consistency:** Notes, review YAML, and both PN mappings are consistent. P4HB is the prototypical PDI: review ACCEPTs GO:0003756 (EXP/IDA/IEA, the canonical core MF) and documents its dual structural-subunit roles (P4H beta-subunit; MTTP). No contradiction.
- **PN story / NEW pressure:** Row 1 GO:0003756 (OLS-verified) is already_in_goa_exact and ACCEPTed — captured. Row 2 GO:0032964 collagen biosynthetic process (OLS-verified real) is flagged new_to_goa. The review captures the collagen role via the **prolyl-4-hydroxylase axis**: GO:0004656 procollagen-proline 4-dioxygenase activity (contributes_to, IDA/TAS), GO:0016222 procollagen-proline 4-dioxygenase complex (part_of), GO:0018401 peptidyl-proline hydroxylation. These are more precise/mechanistic than GO:0032964 (a broad biosynthetic-process umbrella). So the PN's collagen story is biologically real and already mechanistically represented; GO:0032964 itself is a defensible (verified) but broader process-level addition. Conclusion: collagen role already captured at finer granularity; GO:0032964 is a legitimate-but-broader ADD, not strictly needed.
- **Mapping strategy:** Group-level GO:0003756 is the cleanest catalytic-family target (correctly already_in_goa_exact, matching AGR2/ERO1A/ERO1B/ERP27 siblings under the same node — but see the oxidase/non-catalytic caveats for those genes). For the collagen row, GO:0032964 is broader than the review's P4H-complex terms; per the TOMM20/HSPA8/RAB7A "broader-than-review" precedent it risks over-reaching the process when the review's structural-subunit framing (P4HB contributes_to, does not catalyze) is the more accurate model. Prefer the review's GO:0004656/GO:0016222 representation.
- **Evidence alignment:** PN dossier lists no reference titles; alignment is by biology. Review collagen evidence (PMID:7753822, PMID:2846539, both GOA-anchored to GO:0004656/GO:0016222) and PDI evidence (PMID:15720785, 21091435, 32149426) are reviewer-supplied; no shared citation list to compare.
- **Verdict:** Consistent; PDI core validated; collagen role real but already captured via finer P4H-complex terms, making GO:0032964 a broader optional addition. **Recommended edits:** [MAP] consider downgrading the ER-collagen-processing leaf projection (GO:0032964) to context/non-propagating for P4HB (it acts as the non-catalytic structural beta-subunit; the review's GO:0004656 contributes_to + GO:0016222 part_of are the more accurate, already-present representation).