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Transmembrane channel-formation by five complement proteins
Biochemical Society Symposium
|January 1, 1985
Summary
The membrane attack complex (MAC) forms via five serum proteins (C5-C9), creating a pore in cell membranes. This study details the assembly process and the hydrophilic-amphiphilic transition of proteins, particularly C9 polymerization.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- The complement system is crucial for innate and adaptive immunity.
- The membrane attack complex (MAC) is the terminal effector of complement activation.
- MAC formation involves sequential assembly of C5b, C6, C7, C8, and C9.
Purpose of the Study:
- To elucidate the step-by-step assembly of the membrane attack complex (MAC).
- To characterize the structural and functional transitions of complement proteins during MAC formation.
- To investigate the mechanism of C9 polymerization and its role in pore formation.
Main Methods:
- Biochemical analysis of protein interactions.
- Characterization of protein complex formation and stability.
- Investigation of protein conformational changes during assembly.
Main Results:
- The sequential assembly of C5b-C9 into the MAC was detailed.
- A hydrophilic-to-amphiphilic transition was observed during complex formation.
- C9 polymerization was characterized, forming a tubular structure with a 10 nm pore.
Conclusions:
- The study provides a comprehensive understanding of MAC assembly and function.
- The C-terminal portion of C9 is responsible for membrane binding and insertion.
- The C5b-9 complex forms a functional transmembrane channel crucial for complement-mediated cell lysis.