Distinct domains control the addressing and the insertion of Bax into mitochondria.
The translocation of Bax from the cytosol into the mitochondrial outer membrane is a central event during apoptosis. We report that beyond the addressing step, which involves its first alpha-helix (halpha1), the helices alpha5 and alpha6 (halpha5alpha6) are responsible for the insertion of Bax into mitochondrial outer membrane bilayer. The translocation of Bax to mitochondria is associated with specific changes in the conformation of the protein that are under the control of two prolines: Pro-13, which controls the unfolding of halpha1, and Pro-168, a proline located immediately before the hydrophobic carboxyl-terminal end (i.e. helix alpha9, halpha9), which controls the disclosure of halpha5alpha6. An additional step, the disruption of an electrostatic bond formed between Asp-33 (halpha1) and Lys-64 (BH3), allows the mitochondria addressing of Bax. We conclude that, although the intramolecular interactions of halpha1 with the BH3 region control the addressing of Bax to mitochondria, the Pro-168 is involved in the control of its membrane insertion through halpha5alpha6.
Cartron
Pierre-François
PF
Unité Mixte de Recherche 601 INSERM/Université de Nantes, Institut Fédératif de Recherche 26, Equipe 4, Apoptosis & Tumor Progression (Equipe Labellisée Ligue) 9, Quai Moncousu, 44035 Nantes, Cedex 01, France.
Arokium
Hubert
H
Oliver
Lisa
L
Meflah
Khaled
K
Manon
Stephen
S
Vallette
François M
FM
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001224:Aspartic Acid / Q000737:chemistry; D001483:Base Sequence; D002474:Cell-Free System; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D047468:Immunoprecipitation; D008051:Lipid Bilayers; D008099:Liver / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000378:metabolism; D051381:Rats; D055672:Static Electricity; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection; D019076:Transgenes; D020798:Two-Hybrid System Techniques; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D008051:Lipid Bilayers; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D001224:Aspartic Acid; D011392:Proline; D008239:Lysine