Bax-induced cytochrome c release from mitochondria depends on alpha-helices-5 and -6.
The pro-apoptotic protein Bax plays a key role in the mitochondrial signalling pathway. Upon induction of apoptosis, Bax undergoes a conformational change and translocates to mitochondrial membranes, where it inserts and mediates the release of cytochrome c from the intermembrane space into the cytosol. However, the domains of Bax that are essential for the induction of cytochrome c release are still elusive. Therefore various Bax deletion mutants were generated and expressed in Escherichia coli. The proteins were then purified in order to delineate the function of the transmembrane domain, the BH3 (Bcl-2 homology 3) domain and the putative pore-forming alpha-helices-5 and -6. These proteins were used to analyse the mechanism of Bax-induced cytochrome c release from mitochondria. None of the Bax proteins caused cytochrome c release merely through physical perturbation of the mitochondrial outer membrane. The alpha-helices-5 and -6 of Bax were shown to mediate the insertion of the protein into mitochondrial membranes and to be essential for the cytochrome c -releasing activity of Bax. In contrast, neither the transmembrane domain nor a functional BH3 domain is required for the Bax-mediated release of cytochrome c from mitochondria.
Heimlich
Gerd
G
Institute for Medical Microbiology, Immunology and Hygiene, University of Köln, 50935 Köln, Germany.
McKinnon
Alastair D
AD
Bernardo
Katussevani
K
Brdiczka
Dieter
D
Reed
John C
JC
Kain
Renate
R
Krönke
Martin
M
Jürgensmeier
Juliane M
JM
D000818:Animals; D045304:Cytochromes c / Q000378:metabolism*; D005260:Female; D007425:Intracellular Membranes / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D009154:Mutation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D051028:bcl-2-Associated X Protein
C494827:Bax protein, mouse; C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c