4JQZ: Human procaspase-3, crystal form 2

Procaspase-3 (P3) and procaspase-7 (P7) are activated through proteolytic maturation to form caspase-3 (C3) and caspase-7 (C7), respectively, which serve overlapping but nonredundant roles as the executioners of apoptosis in humans. However, it is unclear if differences in P3 and P7 maturation mechanisms underlie their unique biological functions, as the structure of P3 remains unknown. Here, we report structures of P3 in a catalytically inactive conformation, structures of P3 and P7 bound to covalent peptide inhibitors that reveal the active conformation of the zymogens, and the structure of a partially matured C7:P7 heterodimer. Along with a biochemical analysis, we show that P3 is catalytically inactive and matures through a symmetric all-or-nothing process. In contrast, P7 contains latent catalytic activity and matures through an asymmetric and tiered mechanism, suggesting a lower threshold for activation. Finally, we use our structures to design a selection strategy for conformation specific antibody fragments that stimulate procaspase activity, showing that executioner procaspase conformational equilibrium can be rationally modulated. Our studies provide a structural framework that may help to explain the unique roles of these important proapoptotic enzymes, and suggest general strategies for the discovery of proenzyme activators.
PDB ID: 4JQZDownload
MMDB ID: 109930
PDB Deposition Date: 2013/3/20
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 2.889  Å
Source Organism:
Similar Structures:
Biological Unit for 4JQZ: dimeric; determined by author and by software (PISA)
Molecular Components in 4JQZ
Label Count Molecule
Proteins (2 molecules)
Procaspase-3(Gene symbol: CASP3)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB