title: Organization of the mitochondrial apoptotic BAK pore: oligomerization of the BAK homodimers.
abstract: The multidomain pro-apoptotic Bcl-2 family proteins BAK and BAX are believed to form large oligomeric pores in the mitochondrial outer membrane during apoptosis. Formation of these pores results in the release of apoptotic factors including cytochrome c from the intermembrane space into the cytoplasm, where they initiate the cascade of events that lead to cell death. Using the site-directed spin labeling method of electron paramagnetic resonance (EPR) spectroscopy, we have determined the conformational changes that occur in BAK when the protein targets to the membrane and forms pores. The data showed that helices α1 and α6 disengage from the rest of the domain, leaving helices α2-α5 as a folded unit. Helices α2-α5 were shown to form a dimeric structure, which is structurally homologous to the recently reported BAX "BH3-in-groove homodimer." Furthermore, the EPR data and a chemical cross-linking study demonstrated the existence of a hitherto unknown interface between BAK BH3-in-groove homodimers in the oligomeric BAK. This novel interface involves the C termini of α3 and α5 helices. The results provide further insights into the organization of the BAK oligomeric pores by the BAK homodimers during mitochondrial apoptosis, enabling the proposal of a BAK-induced lipidic pore with the topography of a "worm hole."
authors: From the Department of Biochemistry and Molecular Biology, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064.
authors: Sreevidya
authors: S
authors: Aluvila
authors: Tirtha
authors: T
authors: Mandal
authors: Eric
authors: E
authors: Hustedt
authors: Peter
authors: P
authors: Fajer
authors: Jun Yong
authors: JY
authors: Choe
authors: Kyoung Joon
authors: KJ
authors: Oh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000737:chemistry* / Q000378:metabolism*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010539:Permeability; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; D008081:Liposomes; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
keywords: Apoptosis; Bak; Bax; Bcl-2; Cell Death; Electron Paramagnetic Resonance (EPR); Mitochondria; Oligomerization Interface; Spin Labeling