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Increased hemolytic activity of the trypsin-cleaved ninth component of complement
Molecular Immunology
|January 1, 1986
Summary
Limited trypsin cleavage of complement protein C9 (9th component) enhances its hemolytic activity and promotes polymerization. This suggests a shared molecular mechanism underlies both processes, impacting complement system function.
Area of Science:
- Immunology
- Biochemistry
- Complement system
Background:
- The 9th component of complement (C9) is crucial for the formation of the membrane attack complex (MAC).
- Understanding C9's activation and function is key to deciphering complement-mediated cell lysis.
Purpose of the Study:
- To investigate the effects of limited proteolysis on human C9 activity and polymerization.
- To explore the relationship between C9 cleavage, hemolytic activity, and complex formation.
Main Methods:
- Limited proteolysis of human C9 using trypsin.
- Assays to measure hemolytic activity of C9.
- Analysis of C9 polymerization and complex formation (SDS-resistant tubular C9 complexes).
Main Results:
- Trypsin cleavage of C9 yields 53,000 and 20,000 Da fragments.
- Cleaved C9 exhibits a 2.4-fold increase in hemolytic activity compared to untreated C9.
- Trypsinization promotes spontaneous C9 polymerization and formation of SDS-resistant tubular C9 complexes.
Conclusions:
- Specific limited proteolysis of C9 enhances its hemolytic activity.
- Limited proteolysis also induces spontaneous C9 polymerization.
- A similar molecular mechanism likely governs both C9 polymerization and enhanced hemolytic activity.