Related Experiment Videos
Crystal structure of Apaf-1 caspase recruitment domain: an alpha-helical Greek key fold for apoptotic signaling
D E Vaughn1, J Rodriguez, Y Lazebnik
1W. M. Keck Structural Biology, Cold Spring Harbor, NY 11724, USA.
Insights
The Apaf-1 CARD protein structure reveals a novel "death fold" crucial for initiating apoptosis. This discovery aids understanding of cell death signaling pathways.
Area of Science:
- Structural biology
- Molecular and cell biology
- Biochemistry
Background:
- The caspase recruitment domain (CARD) of Apaf-1 interacts with caspase-9's CARD, initiating apoptosis.
- Apoptotic cell death is a critical biological process regulated by protein-protein interactions.
Purpose of the Study:
- To determine the crystal structure of the Apaf-1 CARD.
- To identify conserved structural features and evolutionary relationships of the "death fold".
Main Methods:
- X-ray diffraction at 1.3 Å resolution using a two-element multiwavelength anomalous dispersion (MAD) experiment.
- Structure-based sequence alignment to identify conserved patterns.
Main Results:
- The Apaf-1 CARD adopts a six-helix bundle fold with Greek key topology and a hydrophobic core, termed the "death fold".
- This "death fold" is conserved in other apoptotic signaling domains, despite low sequence identity.
- Conserved patterns characterizing the "death fold" and its subclasses were identified.
Conclusions:
- The "death fold" serves as a rigid scaffold for assembling recognition surfaces in apoptotic signaling.
- Understanding the "death fold" provides insights into the molecular mechanisms of apoptosis.
Abstract:
The caspase recruitment domain (CARD) of Apaf-1 binds to the CARD of caspase-9 to trigger a proteolytic cascade that leads to apoptotic cell death. We report the crystal structure of the Apaf-1 CARD at 1. 3 A resolution, solved in a two-element multiwavelength anomalous dispersion (MAD) X-ray diffraction experiment. This CARD adopts a six-helix bundle fold with Greek key topology surrounding an extensive hydrophobic core. This fold, which we call the "death fold", is found in other domains that mediate interactions in apoptotic signaling despite very low sequence identity. From a structure-based alignment, we identify conserved patterns that characterize the death fold and its subclasses. Like the Ig-fold, it provides a rigid structural scaffold upon which diverse recognition surfaces are assembled.