id: Pfam:PF01027
pfam_id: PF01027
name: Inhibitor of apoptosis-promoting Bax1
short_name: Bax1-I
seed_status: EX_DUF
characterization_status: UNSCORED
curation_status: SEEDED
source_url: https://www.ebi.ac.uk/interpro/api/entry/pfam/PF01027
counters:
  proteins: 27980
  matches: 28281
  proteomes: 13018
  taxa: 23036
  structures: 9
  alphafold_models: 21884
  domain_architectures: 248
provenance:
  snapshot_id: interpro-pfam-duf-2026-10-10
  path: data/worklists/interpro-pfam-duf-2026-10-10.json
  sha256: 17fb625876c9326ed284263a47bcd84e0d7844a31c040dc06cd2260c36f1c383
  generated_at: '2026-10-10T07:44:21.614711Z'
  source_url: https://www.ebi.ac.uk/interpro/api/entry/pfam/
interpro_id: InterPro:IPR006214
description: Programmed cell-death involves a set of Bcl-2 family proteins, some of which inhibit apoptosis
  (Bcl-2 and Bcl-XL) and some of which promote it (Bax and Bak). Human Bax inhibitor, BI-1, is an evolutionarily
  conserved integral membrane protein containing multiple membrane-spanning segments predominantly localised
  to intracellular membranes. It has 6-7 membrane-spanning domains. The C termini of the mammalian BI-1
  proteins are comprised of basic amino acids resembling some nuclear targeting sequences, but otherwise
  the predicted proteins lack motifs that suggest a function. As plant BI-1 appears to localise predominantly
  to the ER, we hypothesised that plant BI-1 could also regulate cell death triggered by ER stress [[cite:PUB00053809]].
  BI-1 appears to exert its effect through an interaction with calmodulin [[cite:PUB00053810]]. The budding
  yeast member of this family has been found unexpectedly to encode a BH3 domain-containing protein (Ybh3p)
  that regulates the mitochondrial pathway of apoptosis in a phylogenetically conserved manner [[cite:PUB00110294]].
  Examination of the crystal structure of a bacterial member of this family shows that these proteins
  mediate a calcium leak across the membrane that is pH-dependent. Calcium homoeostasis balances passive
  calcium leak with active calcium uptake. The structure exists in a pore-closed and pore-open conformation,
  at pHs of 8 and 6 respectively, and the pore can be opened by intracrystalline transition; together
  these findings suggest that pH controls the conformational transition [[cite:PUB00095242]].