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

Srikumar M. Raja, Baikun Wang, Mandakini Dantuluri, Umesh R. Desai, Borries Demeler, Katharina Spiegel, Sunil S. Metkar, Christopher J. Froelich

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96 Scopus citations


We have recently shown that the physiological mediator of granule-mediated apoptosis is a macromolecular complex of granzymes and perforin complexed with the chondroitin-sulfate proteoglycan, serglycin (Metkar, S. S., Wang, B., Aguilar-Santelises, M., Raja, S. M., Uhlin-Hansen, L., Podack, E., Trapani, J. A., and Froelich, C. J. (2002) Immunity 16, 417-428). We now report our biophysical studies establishing the nature of granzyme B-serglycin (GrB·SG) complex. Dynamic laser light scattering studies establish that SG has a hydrodynamic radius of ∼140 ± 23 nm, comparable to some viral particles. Agarose mobility shift gels and surface plasmon resonance (SPR), show that SG binds tightly to GrB and has the capacity to hold 30-60 GrB molecules. SPR studies also indicate equivalent binding affinities (Kd ∼ 0.8 μm), under acidic (granule pH) and neutral isotonic conditions (extra-cytoplasmic pH), for GrB·SG interaction. Finally, characterization of GrB·SG interactions within granules revealed complexes of two distinct molecular sizes, one held ∼4-8 molecules of GrB, whereas the other contained as many as 32 molecules of GrB or other granule proteins. These studies provide a firm biophysical basis for our earlier reported observations that the proapoptotic granzyme is exocytosed predominantly as a macromolecular complex with SG.

Original languageEnglish (US)
Pages (from-to)49523-49530
Number of pages8
JournalJournal of Biological Chemistry
Issue number51
StatePublished - Dec 20 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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