PF01027: Bax1-I

Grounding

PF01027: Inhibitor of apoptosis-promoting Bax1
IPR006214: integrated entry for Inhibitor of apoptosis-promoting Bax1

Source 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 [InterPro reference PUB00053809]. BI-1 appears to exert its effect through an interaction with calmodulin [InterPro reference 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 [InterPro reference 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 [InterPro reference PUB00095242].

Evidence and references

• InterPro entry and its literature references. PUB identifiers are internal InterPro references, not PubMed identifiers. Unresolved citations link to the originating entry.
• Frozen description source: InterPro/Pfam API

Source descriptions and links are provenance, not independent functional validation.

Evidence counts: not scored.

Curated functional assertions

No curated functional assertions supplied.

Protein sequence examples

22 verified sequence examples. FASTA

First 10 shown; the FASTA and family JSON contain all examples.

Pfam membership is not functional evidence. Whole-protein sequences do not establish domain boundaries. A coverage gap here is not absence from UniProt.

Sequences and metadata: UniProt Consortium, CC BY 4.0.

Domain matches

No residue-level domain match evidence is available in this build. Structure and AlphaFold counters do not supply coordinates or establish function.

Snapshot counters

proteins

27,980

matches

28,281

proteomes

13,018

taxa

23,036

structures

9

alphafold models

21,884

domain architectures

248

Classification basis

pfam previous unknown name

No scoring reasons supplied.

Related Mech records

This family joined the worklist after the frozen cross-Mech scan, so other Mechs were not searched for it. Missing links here are not evidence that other Mechs lack it; rows shown come from mentions of a former DUF/UPF name.

No cross-Mech examples are present in the supplied snapshot.

Curation history and reviews

No retained curation events supplied.

No retained review supplied.

Record source

data/families/PF01027.yaml
Family YAML in this build

Download this family (JSON)