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Updated: Jul 30, 2026

Measuring the 50% Haemolytic Complement (CH50) Activity of Serum
08:26

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Published on: March 29, 2010

Decay accelerating activity of complement receptor type 1 (CD35). Two active sites are required for dissociating C5

M Krych-Goldberg1, R E Hauhart, V B Subramanian

  • 1Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

The Journal of Biological Chemistry
|October 26, 1999
PubMed

Insights

This study identified key sites on CR1 (complement receptor 1) that control complement convertase activity. Site 1 is crucial for C3 convertase dissociation, while both Site 1 and Site 2 are needed for efficient C5 convertase regulation.

Area of Science:

  • Immunology
  • Complement System Biology

Background:

  • The complement system is a crucial part of innate immunity.
  • Complement receptor 1 (CR1) plays a regulatory role in complement activation.
  • Understanding CR1's function in C3 and C5 convertase regulation is vital.

Purpose of the Study:

  • To pinpoint the specific regions within CR1 responsible for dissociating C3 and C5 convertases.
  • To characterize the distinct roles of different CR1 domains in complement regulation.

Main Methods:

  • Generation of truncated CR1 derivatives containing complement control protein repeats (CCPs).
  • Assays to measure decay accelerating activity on C3 and C5 convertases.
  • Homologous substitution mutagenesis to identify critical residues.

Main Results:

  • Site 1 (CCPs 1-3) effectively accelerates the decay of C3 convertases.
  • Site 2 exhibits lower C3 convertase decay activity compared to Site 1.
  • Efficient C5 convertase decay requires both Site 1 and Site 2, with Site 1 being primary.
  • Mutagenesis identified key residues in Site 1 for dissociation activity.

Conclusions:

  • CR1's Site 1 is the primary mediator of C5 convertase decay acceleration.
  • Site 2 plays an auxiliary role in C5 convertase regulation, potentially via C3b binding.
  • Engineered CR1 variants show enhanced C3 convertase decay accelerating activity.

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