BIR

Baculoviral inhibition of apoptosis protein repeat		 BIR
SMART accession number:SM00238
Description: Domain found in inhibitor of apoptosis proteins (IAPs) and other proteins. Acts as a direct inhibitor of caspase enzymes.
Interpro abstract (IPR001370):

The 'baculovirus inhibitior of apoptosis protein repeat' (BIR) [ (PUBMED:8139034) (PUBMED:8552191) ] is a domain of about 70 residues arranged in tandem repeats separated by a variable length linker, that seems to confer cell death-preventing activity. It is found in proteins belonging to the IAP (inhibitor of apoptosis proteins) family. The critical motifs required for anti-apoptotic activity of IAP proteins are the BIRs. All IAP proteins contain from one to three BIRs, and all known interactions between IAPs and other proteins are mediated by one or more BIRs [ (PUBMED:10404221) ]. In higher eukaryotes, BIR domains inhibit apoptosis by acting as direct inhibitors of the caspase family of protease enzymes. Proteins with BIR domains are considered peptidase inhibitors in family I32. In yeast, BIR domains are involved in regulating cytokinesis. This novel fold is stabilized by zinc tetrahedrally coordinated by one histidine and three cysteine residues and resembles a classical zinc finger [ (PUBMED:8445726) ].

The BIR domain has a fold that is stabilised by zinc tetrahedrally coordinated by one histidine and three cysteine residues. The structure consists of three short alpha-helices and turns with the zinc packed in an unusually hydrophobic environment created by residues that are highly conserved among all BIRs. A subclass of repeats, comprising those at the C terminus of a series of BIR repeats from IAP proteins bearing RING finger domains, are likely to contain a C-terminal region that form an alpha-helix [ (PUBMED:10404221) ].

Proteins that are known to contain this domain include:

  • Baculoviruses apoptosis inhibitors (IAPs).
  • Mammalian apoptosis inhibitors 1 and 2 (IAP1 and IAP2; BIRC-2 and BIRC-3; MEROPS identifiers I32.002 and I32.003, respectively).
  • Mammalian X-linked inhibitor of apoptosis protein (X-linked IAP; MEROPS identifier I32.004).
  • Chicken IAP (ITA).
  • Human neuronal apoptosis inhibitory protein (NAIP, BIRC-1; MEROPS identifier I32.001).
  • Drosophila apoptosis inhibitors 1 and 2 (Iap1 and Iap2; MEROPS identifiers I32.009 and I32.011, respectively)).
  • African Swine Fever Virus (ASFV) protein p27.
Family alignment:
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There are 10317 BIR domains in 5952 proteins in SMART's nrdb database.

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