An exegesis of IAPs: salvation and surprises from BIR motifs

Trends Cell Biol. 1999 Aug;9(8):323-8. doi: 10.1016/s0962-8924(99)01609-8.


The BIR (baculovirus IAP repeat) motif is a conserved sequence of approximately 70 amino acids that was identified originally in the 'inhibitor of apoptosis' (IAP) family of proteins. BIR-containing proteins (BIRPs) are found in viruses, yeast and metazoans. Recent genetic analysis of a nematode BIRP demonstrated an essential role in cytokinesis instead of apoptosis. It is likely that BIRs originated in eukaryotes to serve a role in cytokinesis and/or mitotic spindle function during cell division and that, with gene duplication, the more recent adaptation of some BIRPs to the regulation of apoptosis was possible. IAPs interact with a variety of proteins, including members of the caspase protease family. This article discusses current research on the structure and function of the BIR motifs and how it could provide insight into the function of BIRPs in cell division.

Publication types

  • Review

MeSH terms

  • Animals
  • Apoptosis*
  • Caspase Inhibitors
  • Conserved Sequence
  • Inhibitor of Apoptosis Proteins
  • Microtubule-Associated Proteins*
  • Models, Biological
  • Neoplasm Proteins
  • Nucleopolyhedroviruses*
  • Proteins / physiology
  • Signal Transduction
  • Spindle Apparatus / physiology
  • Survivin
  • Viral Proteins*


  • BIRC5 protein, human
  • Caspase Inhibitors
  • Inhibitor of Apoptosis Proteins
  • Microtubule-Associated Proteins
  • Neoplasm Proteins
  • Proteins
  • Survivin
  • Viral Proteins
  • inhibitor of apoptosis, Nucleopolyhedrovirus