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Structural asymmetry of procaspase-7 bound to a specific inhibitor

Hyo Jin Kang1, Young-mi Lee, Kwang-Hee Bae

  • 1Department of Chemistry, College of Natural Science, Dongguk University, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Republic of Korea.

Acta Crystallographica. Section D, Biological Crystallography
|July 31, 2013
PubMed

Insights

Procaspase-7 exhibits intrinsic catalytic activity, enabling auto-activation. Structural analysis reveals that L2 loops in homodimeric procaspase-7 form a complete active site, shedding light on caspase-7 activation mechanisms.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Caspase-7 is a key enzyme in apoptosis, activated by initiator caspases.
  • The precise mechanism of caspase-7 activation remains incompletely understood.
  • Procaspase-7 demonstrates auto-activation during overexpression, suggesting inherent catalytic activity.

Purpose of the Study:

  • To investigate the intrinsic catalytic activity of procaspase-7.
  • To elucidate the structural basis of procaspase-7 auto-activation and its interaction with inhibitors.
  • To gain insights into the folding mechanism and basal activity of procaspase-7.

Main Methods:

  • Site-directed mutagenesis to create procaspase-7 variants with altered L2 loops.
  • Enzyme kinetics assays to determine catalytic activity and inhibition.
  • X-ray crystallography to solve the three-dimensional structure of procaspase-7 variants bound to Ac-DEVD-CHO.

Main Results:

  • A procaspase-7 variant with a six-amino-acid insertion in the L2 loop exhibited significant catalytic activity, inhibited by Ac-DEVD-CHO.
  • The crystal structure of homodimeric procaspase-7 bound to Ac-DEVD-CHO revealed asymmetry.
  • The L2 loops from both monomers collaborated to form a complete active site, with one monomer's active site being incomplete.

Conclusions:

  • Procaspase-7 possesses inherent catalytic activity, facilitated by its L2 loops.
  • The L2 loops act as integral components of the active site in homodimeric procaspase-7.
  • These findings provide the first structural view of a procaspase-7 variant-inhibitor complex, illuminating caspase activation pathways.
Keywords:
caspase-7 activationinhibitorsprocaspase-7

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