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The structure of XIAP BIR2: understanding the selectivity of the BIR domains

Christine Lukacs1, Charles Belunis, Robert Crowther

  • 1Discovery Technologies, Hoffmann-La Roche, 340 Kingsland Street, Nutley, NJ 07110, USA.

Acta Crystallographica. Section D, Biological Crystallography
|September 4, 2013
PubMed

Insights

This study details the crystal structures of XIAP BIR2 domain complexes, revealing insights into designing selective inhibitors for cancer therapy by targeting apoptosis pathways.

Area of Science:

  • Structural biology
  • Molecular mechanisms of apoptosis
  • Drug discovery for cancer

Background:

  • The inhibitor of apoptosis protein (XIAP) is crucial in regulating apoptosis.
  • Targeting XIAP's BIR domains offers a strategy for cancer treatment by modulating apoptosis.
  • Selective inhibition of XIAP BIR2-caspase-3 interaction could block the extrinsic apoptotic pathway.

Purpose of the Study:

  • To elucidate the structural basis for selective inhibition of the XIAP BIR2 domain.
  • To understand the structural elements driving selectivity between XIAP BIR2 and BIR3 domains.
  • To guide the design of novel BIR2-selective inhibitors for cancer therapy.

Main Methods:

  • Crystallization of the XIAP BIR2 apo domain.
  • Soaking peptides and small molecules into BIR2 crystals.
  • High-resolution X-ray diffraction analysis.
  • Comparative structural analysis of BIR2 apo and complex structures with XIAP BIR3.

Main Results:

  • The crystal structure of the XIAP BIR2 apo domain was determined.
  • Structures of five BIR2-tetrapeptide complexes were solved.
  • Structural flexibility within BIR2 was observed and analyzed.
  • Key structural differences between BIR2 and BIR3 were identified, explaining selectivity.

Conclusions:

  • Understanding XIAP BIR2 structural flexibility and its differences from BIR3 is key to designing selective inhibitors.
  • These findings provide a foundation for developing targeted cancer therapies by inhibiting the extrinsic apoptotic pathway.
  • The study offers a rational design strategy for BIR2-selective small-molecule inhibitors.
Keywords:
AVPIBIR domainsSMACXIAPapoptosiscaspasesextrinsic pathwayinhibitor of apoptosispeptide complex

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