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A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl
05:20

A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl

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Cytotoxic cell granule-mediated apoptosis. Characterization of the macromolecular complex of granzyme B with

Srikumar M Raja1, Baikun Wang, Mandakini Dantuluri

  • 1Department of Medicine, Evanston Northwestern Healthcare Research Institute, 2650 Ridge Avenue, Evanston, Illinois 60201, USA. s-raja@northwestern.edu

The Journal of Biological Chemistry
|October 22, 2002
PubMed

Insights

This study reveals that serglycin (SG) forms large complexes with granzyme B (GrB), acting as a scaffold that binds many GrB molecules. These findings explain how GrB is released in a pre-assembled, active form for apoptosis.

Area of Science:

  • Immunology
  • Molecular Biology
  • Biophysics

Background:

  • Granule-mediated apoptosis involves granzymes and perforin.
  • Serglycin (SG) is a chondroitin-sulfate proteoglycan found in cytotoxic granules.

Purpose of the Study:

  • To elucidate the biophysical properties of the granzyme B-serglycin (GrB.SG) complex.
  • To understand the molecular interactions governing GrB packaging and release.

Main Methods:

  • Dynamic laser light scattering (DLLS) to determine SG size.
  • Agarose gel electrophoresis and surface plasmon resonance (SPR) to analyze GrB.SG binding.
  • Characterization of GrB.SG complexes within granules.

Main Results:

  • SG exhibits a large hydrodynamic radius (~140 nm), similar to viral particles.
  • SG tightly binds GrB, with a capacity to hold 30-60 GrB molecules per SG.
  • GrB.SG binding affinity is consistent across acidic (granule) and neutral (extracellular) pH.
  • Granules contain GrB.SG complexes of varying sizes, holding 4-8 or up to 32 GrB molecules.

Conclusions:

  • Biophysical studies confirm SG acts as a scaffold for GrB.
  • The GrB.SG complex is pre-formed within granules, facilitating efficient exocytosis of active granzyme.
  • These findings provide a molecular basis for granzyme release during apoptosis.

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