Baculoviral inhibition of apoptosis protein repeat
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)].

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).
  • Mammalian X-linked inhibitor of apoptosis protein (X-linked IAP).
  • Chicken IAP (ITA).
  • Human neuronal apoptosis inhibitory protein (NAIP).
  • Drosophila apoptosis inhibitors 1 and 2 (Iap1 and Iap2).
  • African Swine Fever Virus (ASFV) protein p27.
Family alignment:
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There are 3116 BIR domains in 1782 proteins in SMART's nrdb database.

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