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The BH3 domain of Bax is essential for regulating its solubility and mitochondrial targeting
Author(s) -
Zhou Hui,
Hou Qi,
Hsu Yite
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a118-c
Subject(s) - mitochondrion , mutant , amino acid , microbiology and biotechnology , apoptosis , alanine , cytochrome c , bcl 2 associated x protein , biology , cytosol , programmed cell death , biochemistry , chemistry , gene , caspase 3 , enzyme
The pro‐apoptotic protein Bax plays an important role in apoptosis regulation. In response to many apoptotic stimuli, Bax translocates from cytosol to mitochondria and triggers mitochondrial dysfunctions. The BH3 domain of Bax (a.a 59–73) has been identified to be an essential domain of the protein. It enables Bax bind to the pro‐survival protein Bcl‐2 or Bcl‐XL and has been shown to be important for its death‐prohibitory property. Here we reported that the BH3 domain is important for regulating Bax solubility and mitochondria targeting. By mutagenizing individual amino acids within this domain and tagging each mutant to GFP, we found that two amino acid residues, L70 and D71, appear to be critical in regulating Bax solubility. Substitution of these amino acids with alanine resulted in the constitutive localization of these mutants to mitochondria. Expression of these mutants in Cos‐7 cells lead to the release of cytochrome c and cell death. Interestingly, unlike wild‐type Bax, co‐expression of these mutants with Bcl‐2 or Bcl‐XL didn’t inhibit their localization to mitochondria, although these mutants bind equally well to Bcl‐2 or Bcl‐XL as the wt‐Bax. Moreover, we have identified four amino acids within this domain that are responsible for the selective targeting of Bax to mitochodria. Replacement of these amino acids with alanine resulted in the concomitant localization of Bax to both mitochondria and ER. In summary, we have identified a novel function of the BH3 domain of Bax. This research is supported by the NIH grant RO1 NS40932.