Proteolysis of the monomeric and dimeric C5b-9 complexes of complement: Alteration in the susceptibility to proteases of the C9 subunits associated with C5b-9 dimerization

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Abstract

The C5b-9 monomer having the sedimentation coefficient of 23S was extracted from the rabbit erythrocyte membranes that had been treated with a limiting amount of C9-deficient human serum and of 125I-C9. Upon proteolysis by trypsin and chymotrypsin, the C9 subunits of this complex were cleaved by these enzymes at multiple sites, yielding fragments with m.w. ranging from 40,000 to 19,000. The uncomplexed C9 was also cleaved by both enzymes at multiple sites. By contrast, the C9 subunits of the C5b-9 dimer were found to be totally insusceptible to chymotrypsin under the conditions studied (37°C; 24 hr) and only partially susceptible to trypsin (33% of the C9 subunits were cleaved by trypsin into 2 fragments during incubation at 37°C for up to 24 hr). Therefore, these results indicate that, although the binding of C9 molecules to the C5b-8 complex (C5b-9 monomer formation) does not significantly affect the susceptibility to proteases of the C9 molecules, C5b-9 dimer formation markedly limits the accessibility of proteases to the C9 subunit molecules. An implication of this finding to a role for C9 in C5b-9 dimerization is discussed.

Original languageEnglish
Pages (from-to)423-426
Number of pages4
JournalJournal of Immunology
Volume127
Issue number2
Publication statusPublished - 1981
Externally publishedYes

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Complement Membrane Attack Complex
Dimerization
Proteolysis
Peptide Hydrolases
Trypsin
Chymotrypsin
Erythrocyte Membrane
Enzymes
Rabbits
Serum

ASJC Scopus subject areas

  • Immunology

Cite this

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title = "Proteolysis of the monomeric and dimeric C5b-9 complexes of complement: Alteration in the susceptibility to proteases of the C9 subunits associated with C5b-9 dimerization",
abstract = "The C5b-9 monomer having the sedimentation coefficient of 23S was extracted from the rabbit erythrocyte membranes that had been treated with a limiting amount of C9-deficient human serum and of 125I-C9. Upon proteolysis by trypsin and chymotrypsin, the C9 subunits of this complex were cleaved by these enzymes at multiple sites, yielding fragments with m.w. ranging from 40,000 to 19,000. The uncomplexed C9 was also cleaved by both enzymes at multiple sites. By contrast, the C9 subunits of the C5b-9 dimer were found to be totally insusceptible to chymotrypsin under the conditions studied (37°C; 24 hr) and only partially susceptible to trypsin (33{\%} of the C9 subunits were cleaved by trypsin into 2 fragments during incubation at 37°C for up to 24 hr). Therefore, these results indicate that, although the binding of C9 molecules to the C5b-8 complex (C5b-9 monomer formation) does not significantly affect the susceptibility to proteases of the C9 molecules, C5b-9 dimer formation markedly limits the accessibility of proteases to the C9 subunit molecules. An implication of this finding to a role for C9 in C5b-9 dimerization is discussed.",
author = "Ken-ichi Yamamoto and S. Migita",
year = "1981",
language = "English",
volume = "127",
pages = "423--426",
journal = "Journal of Immunology",
issn = "0022-1767",
publisher = "American Association of Immunologists",
number = "2",

}

TY - JOUR

T1 - Proteolysis of the monomeric and dimeric C5b-9 complexes of complement

T2 - Alteration in the susceptibility to proteases of the C9 subunits associated with C5b-9 dimerization

AU - Yamamoto, Ken-ichi

AU - Migita, S.

PY - 1981

Y1 - 1981

N2 - The C5b-9 monomer having the sedimentation coefficient of 23S was extracted from the rabbit erythrocyte membranes that had been treated with a limiting amount of C9-deficient human serum and of 125I-C9. Upon proteolysis by trypsin and chymotrypsin, the C9 subunits of this complex were cleaved by these enzymes at multiple sites, yielding fragments with m.w. ranging from 40,000 to 19,000. The uncomplexed C9 was also cleaved by both enzymes at multiple sites. By contrast, the C9 subunits of the C5b-9 dimer were found to be totally insusceptible to chymotrypsin under the conditions studied (37°C; 24 hr) and only partially susceptible to trypsin (33% of the C9 subunits were cleaved by trypsin into 2 fragments during incubation at 37°C for up to 24 hr). Therefore, these results indicate that, although the binding of C9 molecules to the C5b-8 complex (C5b-9 monomer formation) does not significantly affect the susceptibility to proteases of the C9 molecules, C5b-9 dimer formation markedly limits the accessibility of proteases to the C9 subunit molecules. An implication of this finding to a role for C9 in C5b-9 dimerization is discussed.

AB - The C5b-9 monomer having the sedimentation coefficient of 23S was extracted from the rabbit erythrocyte membranes that had been treated with a limiting amount of C9-deficient human serum and of 125I-C9. Upon proteolysis by trypsin and chymotrypsin, the C9 subunits of this complex were cleaved by these enzymes at multiple sites, yielding fragments with m.w. ranging from 40,000 to 19,000. The uncomplexed C9 was also cleaved by both enzymes at multiple sites. By contrast, the C9 subunits of the C5b-9 dimer were found to be totally insusceptible to chymotrypsin under the conditions studied (37°C; 24 hr) and only partially susceptible to trypsin (33% of the C9 subunits were cleaved by trypsin into 2 fragments during incubation at 37°C for up to 24 hr). Therefore, these results indicate that, although the binding of C9 molecules to the C5b-8 complex (C5b-9 monomer formation) does not significantly affect the susceptibility to proteases of the C9 molecules, C5b-9 dimer formation markedly limits the accessibility of proteases to the C9 subunit molecules. An implication of this finding to a role for C9 in C5b-9 dimerization is discussed.

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