title: Transient binding of an activator BH3 domain to the Bak BH3-binding groove initiates Bak oligomerization.
abstract: The mechanism by which the proapoptotic Bcl-2 family members Bax and Bak release cytochrome c from mitochondria is incompletely understood. In this paper, we show that activator BH3-only proteins bind tightly but transiently to the Bak hydrophobic BH3-binding groove to induce Bak oligomerization, liposome permeabilization, mitochondrial cytochrome c release, and cell death. Analysis by surface plasmon resonance indicated that the initial binding of BH3-only proteins to Bak occurred with similar kinetics with or without detergent or mitochondrial lipids, but these reagents increase the strength of the Bak-BH3-only protein interaction. Point mutations in Bak and reciprocal mutations in the BH3-only proteins not only confirmed the identity of the interacting residues at the Bak-BH3-only protein interface but also demonstrated specificity of complex formation in vitro and in a cellular context. These observations indicate that transient protein-protein interactions involving the Bak BH3-binding groove initiate Bak oligomerization and activation.
authors: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA.
authors: Haiming
authors: H
authors: Dai
authors: Alyson
authors: A
authors: Smith
authors: X Wei
authors: XW
authors: Meng
authors: Paula A
authors: PA
authors: Schneider
authors: Yuan-Ping
authors: YP
authors: Pang
authors: Scott H
authors: SH
authors: Kaufmann
mesh_terms: D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000737:chemistry* / Q000172:deficiency / Q000378:metabolism*
chemical_list: C494772:BAK1 protein, human; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein