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Related Experiment Videos

The structure of bovine complement component 3 reveals the basis for thioester function.

Folmer Fredslund1, Lasse Jenner, Lise B Husted

  • 1Department of Molecular Biology, University of Aarhus, Denmark.

Journal of Molecular Biology
|July 13, 2006
PubMed
Summary

The structure of bovine complement component 3 (C3) reveals how its thioester bond becomes accessible for activation. This finding provides insights into the complement system

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Area of Science:

  • Structural Biology
  • Immunology
  • Biochemistry

Background:

  • The third component of complement (C3) is a critical glycoprotein in the complement response.
  • C3 consists of alpha and beta chains linked by a disulfide bridge, with an internal thioester crucial for activation.

Purpose of the Study:

  • To determine the high-resolution structure of bovine C3.
  • To elucidate the structural basis of C3 activation and thioester reactivity.

Main Methods:

  • X-ray crystallography of bovine C3.
  • Structural analysis at 3 Angstroms resolution.

Main Results:

  • The structure reveals the thioester is buried between the thioester and properdin binding domains.

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  • Upon activation, the domain interface breaks, exposing the thioester.
  • A helical transition in the main chain around the thioester is observed, explaining its reactivity.

    • Conclusions:

    • The bovine C3 structure explains the mechanism of thioester exposure and reactivity during complement activation.
    • A conserved glutamate residue may play a catalytic role.
    • The findings suggest potential targets for C3 activation inhibitors.