title: Three-dimensional structure of a double apoptosome formed by the Drosophila Apaf-1 related killer.
abstract: The Drosophila Apaf-1 related killer (Dark) forms an apoptosome that activates Dronc, an apical procaspase in the intrinsic cell death pathway. To study this process, we assembled a large Dark complex in the presence of dATP. Remarkably, we found that cytochrome c was not required for assembly and when added, cytochrome c did not bind to the Dark complex. We then determined a 3D structure of the Dark complex at 18.8A resolution using electron cryo-microscopy and single particle methods. In the structure, eight Dark subunits form a wheel-like particle and two of these rings associate face-to-face. In contrast, Apaf-1 forms a single ring that is comprised of seven subunits and each Apaf-1 binds a molecule of cytochrome c. We then used relevant crystal structures to model the Dark complex. This analysis shows that a single Dark ring and the Apaf-1 apoptosome share many key features. When taken together, the data suggest that a single ring in the Dark complex may represent the Drosophila apoptosome. Thus, our analysis provides a domain model of this complex and gives insights into its function.
authors.affiliation: Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany St., Boston, MA 02118-2526, USA.
authors.forename: Xinchao
authors.initials: X
authors.lastname: Yu
authors.forename: Lai
authors.initials: L
authors.lastname: Wang
authors.forename: Devrim
authors.initials: D
authors.lastname: Acehan
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Wang
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Akey
mesh_terms: D000818:Animals; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D020285:Cryoelectron Microscopy; D045304:Cytochromes c / Q000737:chemistry; D004330:Drosophila / Q000737:chemistry*; D029721:Drosophila Proteins / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry*; D008958:Models, Molecular; D021122:Protein Subunits / Q000737:chemistry; D011506:Proteins / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D011506:Proteins; C400550:dark protein, Drosophila; D045304:Cytochromes c