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Related Experiment Videos

Structure and function of C1r and C1s: current concepts.

G J Arlaud1, N M Thielens, C A Aude

  • 1Départment de Recherches Fondamentales Unité INSERM 238, Centre d'Etudes Nucléaires de Grenoble, France.

Behring Institute Mitteilungen
|July 1, 1989
PubMed
Summary

Complement C1r and C1s are homologous serine proteases with similar structures but distinct glycosylation. Their activation involves a single bond cleavage, forming active enzymes crucial for the complement system.

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The role of the individual domains in the structure and function of the catalytic region of a modular serine protease, C1r.

Journal of immunology (Baltimore, Md. : 1950)·2001

Area of Science:

  • Biochemistry
  • Immunology
  • Structural Biology

Background:

  • C1r and C1s are homologous serine proteases and the catalytic core of the C1 complex in the complement system.
  • Both proteins are activated via cleavage of a single Arg-Ile bond, converting single-chain proenzymes to active two-chain enzymes linked by a disulfide bridge.
  • Their NH2-terminal A chains contain unique structural units and repeats homologous to complement proteins, while COOH-terminal B chains resemble serine protease catalytic chains but lack a key disulfide bridge.

Purpose of the Study:

  • To compare the structural organization and activation patterns of C1r and C1s.
  • To investigate the sequence homology and differences between C1r and C1s.
  • To analyze the glycosylation patterns of C1r and C1s.

Main Methods:

Related Experiment Videos

  • Sequence comparison of C1r and C1s.
  • Analysis of structural units and repeat regions.
  • Examination of glycosylation sites.

    • Main Results:

    • C1r and C1s share 40% amino acid identity and conserved cysteine residues.
    • Both proteins possess distinct NH2-terminal structural units, including EGF-like segments and internal repeats.
    • Significant differences were observed in glycosylation patterns, with C1r having four sites and C1s having two.

    Conclusions:

    • C1r and C1s exhibit conserved structural features and activation mechanisms characteristic of serine proteases.
    • Despite high sequence homology, distinct glycosylation patterns suggest functional or regulatory differences.
    • Understanding these structural and functional distinctions is vital for comprehending the complement system's initiation and regulation.