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Related Experiment Videos

The relationship between polymerization of complement component C9 and membrane channel formation.

R G DiScipio1

  • 1Research Institute of Scripps Clinic, Department of Immunology, La Jolla, CA 92037.

Journal of Immunology (Baltimore, Md. : 1950)
|December 15, 1991
PubMed
Summary

Complement C9 polymerization, triggered by low ionic strength and calcium, leads to membrane channel formation. This process involves a reversible hydrophilic-to-amphiphilic transition, exposing binding sites and enabling cytolysis.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • The complement system plays a crucial role in innate and adaptive immunity.
  • Complement C9 is the final component that polymerizes to form the membrane attack complex (MAC).
  • Understanding C9 polymerization is key to elucidating MAC function and potential therapeutic targets.

Purpose of the Study:

  • To investigate the relationship between C9 polymerization and membrane channel formation.
  • To identify conditions influencing C9 polymerization and its molecular transitions.
  • To establish the functional link between C9 polymerization and cytolytic activity.

Main Methods:

  • Studied C9 polymerization under varying ionic strength, calcium concentrations, and temperatures.

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  • Measured C9 binding to hydrophobic and hydrophilic supports and erythrocytes.
  • Utilized radiolabeling to compare C9 forms and identify exposed membrane-binding sites.

    • Main Results:

    • C9 polymerization is favored by low ionic strength and calcium ions, dependent on C9 concentration.
    • Calcium ions enhance C9 self-association affinity and induce reversible amphiphilic properties at 0°C.
    • Polymerization at 37°C results in permanent hydrophilic-to-amphiphilic transition and poly(C9) formation, enabling erythrocyte lysis.

    Conclusions:

    • Circular polymerization of C9 induces a critical hydrophilic-to-amphiphilic transition.
    • This transition is essential for membrane perforation and the formation of functional C9 channels.
    • The study reveals that polymerization exposes the membrane-binding site of C9.