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In Vivo Biosensor Tracks Non-apoptotic Caspase Activity in Drosophila
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Three-dimensional structure of a double apoptosome formed by the Drosophila Apaf-1 related killer

Xinchao Yu1, Lai Wang, Devrim Acehan

  • 1Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany St., Boston, MA 02118-2526, USA.

Journal of Molecular Biology
|November 29, 2005
PubMed

Insights

The Drosophila Apaf-1 related killer (Dark) forms an apoptosome crucial for intrinsic cell death. Researchers discovered cytochrome c is not required for Dark complex assembly, challenging previous models of apoptosis.

Area of Science:

  • Cell biology
  • Molecular biology
  • Biochemistry

Background:

  • The intrinsic cell death pathway is regulated by apoptosomes.
  • Drosophila Apaf-1 related killer (Dark) is essential for activating Dronc, a key procaspase in this pathway.
  • Understanding apoptosome assembly and function is critical for cell death research.

Purpose of the Study:

  • To investigate the assembly and structure of the Drosophila apoptosome.
  • To determine the role of cytochrome c in Dark complex formation.
  • To elucidate the functional mechanism of the Dark complex in apoptosis.

Main Methods:

  • Assembly of the large Dark complex in the presence of dATP.
  • Cryo-electron microscopy and single particle analysis to determine the 3D structure.
  • Modeling of the Dark complex using existing crystal structures.

Main Results:

  • Cytochrome c is not required for Dark complex assembly and does not bind to it.
  • The 3D structure reveals eight Dark subunits forming a wheel-like particle, with two rings associated face-to-face.
  • Structural analysis indicates a single Dark ring shares features with the Apaf-1 apoptosome.

Conclusions:

  • A single ring within the Dark complex likely represents the functional Drosophila apoptosome.
  • The study provides a domain model of the Dark complex, offering insights into its apoptotic function.
  • Findings challenge the universal requirement of cytochrome c for apoptosome assembly.

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