Structure of and influence of a tick complement inhibitor on human complement component 5

Nat Immunol. 2008 Jul;9(7):753-60. doi: 10.1038/ni.1625. Epub 2008 Jun 8.


To provide insight into the structural and functional properties of human complement component 5 (C5), we determined its crystal structure at a resolution of 3.1 A. The core of C5 adopted a structure resembling that of C3, with the domain arrangement at the position corresponding to the C3 thioester being very well conserved. However, in contrast to C3, the convertase cleavage site in C5 was ordered and the C345C domain flexibly attached to the core of C5. Binding of the tick C5 inhibitor OmCI to C5 resulted in stabilization of the global conformation of C5 but did not block the convertase cleavage site. The structure of C5 may render possible a structure-based approach for the design of new selective complement inhibitors.

MeSH terms

  • Animals
  • Arthropod Proteins
  • Binding Sites
  • Carrier Proteins
  • Complement C3
  • Complement C5 / chemistry*
  • Complement C5 / metabolism*
  • Crystallography, X-Ray
  • Humans
  • Insect Proteins / chemistry
  • Insect Proteins / metabolism*
  • Protein Structure, Quaternary*
  • Surface Plasmon Resonance


  • Arthropod Proteins
  • Carrier Proteins
  • Complement C3
  • Complement C5
  • Insect Proteins
  • OmCI protein, tick

Associated data

  • PDB/3CU7