## ATP6V1B1
- **UniProt:** P15313 · **batch:** proteostasis-batch-2026-06-07 · **review status:** COMPLETE
- **PN placement:** two ALP leaves "V1 lysosomal v-ATPase proton pump component" (Nutrient sensing; Lysosomal acidification). **PN-node mapping:** leaf→GO:0046612 lysosomal V1 domain (more_specific_than_existing_goa); leaf→GO:0033176 V-type ATPase complex (entailed_by_goa_closure); type→GO:0007042 lysosomal lumen acidification (more_specific_than_existing_goa).
- **Consistency:** PARTIAL CONFLICT. Deep research/notes and the review establish B1 as the kidney/inner-ear-restricted, non-catalytic B subunit whose functionally relevant site is the **apical plasma membrane** (intercalated cells; IDA PMID:16769747, PMID:29993276), driving urinary acid secretion (renal tubular secretion, dRTA; PMID:12414817). The review explicitly MARKs_AS_OVER_ANNOTATED a synaptic-vesicle annotation as an inappropriate cross-isoform transfer, and never asserts a lysosomal role. The PN places B1 under "lysosomal v-ATPase" and projects **lysosomal** lumen acidification + lysosomal V1 domain — which the gene biology does not support. PN Notes ("V1 cytosolic component … pumps protons into the lysosome") mis-frame this plasma-membrane isoform.
- **PN story / NEW pressure:** PN's lysosomal acidification claim OVER-REACHES for B1. GO:0046612/GO:0007042 are verified real but are the wrong specialization: B1's evidenced compartment is apical plasma membrane, not lysosome. Already captured (correctly) by review: GO:0016324 apical plasma membrane, GO:0097254 renal tubular secretion, GO:0006885 regulation of pH. **Lysosomal projection should NOT be propagated to B1.**
- **Mapping strategy:** The shared V-ATPase node maps to lysosomal terms generically, but B1 is a tissue-restricted plasma-membrane isoform — analogous to the TOMM20/HSPA8/RAB7A "too broad" precedent. **[MAP]** flag B1 as an exception to lysosomal projection (scope=too_broad/wrong_compartment for this isoform); the generic vacuolar V1 term (GO:0000221, already in review) is the safe target.
- **Evidence alignment:** No overlap. PN cites generic V-ATPase/mTORC1 reviews; review is richly sourced with B1-specific genetics/structure (PMID:12414817, 16769747, 29993276, 33065002, 9916796). Review strongly better-evidenced.
- **Verdict:** OVER-REACH — PN lysosomal projection (GO:0046612/GO:0007042) is wrong-compartment for this apical-plasma-membrane kidney isoform. **Recommended edits:** [MAP] exempt ATP6V1B1 from lysosomal-acidification/lysosomal-V1 projection; restrict to vacuolar V1 domain + plasma-membrane/renal acid-secretion terms already in the review.