BAX Inhibitor-1, an ancient cell death suppressor in animals and plants with prokaryotic relatives

Apoptosis. 2004 May;9(3):299-307. doi: 10.1023/b:appt.0000025806.71000.1c.


BAX Inhibitor-1 (BI-1) was originally described as testis enhanced gene transcript in mammals. Functional screening in yeast for human proteins that can inhibit the cell death provoking function of BAX, a proapoptotic Bcl-2 family member, led to functional characterisation and renaming of BI-1. The identification of functional homologues of BI-1 in plants and yeast widened the understanding of BI-1 function as an ancient suppressor of programmed cell death. BI-1 is one of the few cell death suppressors conserved in animals and plants. Computer predictions and experimental data together suggest that BI-1 is a membrane spanning protein with 6 to 7 transmembrane domains and a cytoplasmic C-terminus sticking in the endoplasmatic reticulum and nuclear envelope. Proteins similar to BI-1 are present in other eukaryotes, bacteria, and even viruses encode BI-1 like proteins. BI-1 is involved in development, response to biotic and abiotic stress and probably represents an indispensable cell protectant. BI-1 appears to suppress cell death induced by mitochondrial dysfunction, reactive oxygen species or elevated cytosolic Ca(2+) levels. This review focuses on the present understanding about BI-1 and suggests potential directions for further analyses of this increasingly noticed protein.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis / drug effects*
  • Cytoplasm / chemistry
  • Endoplasmic Reticulum / chemistry
  • Humans
  • Immunity, Innate
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Nuclear Envelope / chemistry
  • Phylogeny
  • Plants
  • Prokaryotic Cells / metabolism*
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Sequence Homology, Amino Acid
  • Subcellular Fractions
  • Terminology as Topic
  • Tissue Distribution
  • bcl-2-Associated X Protein


  • BAX protein, human
  • Membrane Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2-Associated X Protein