Kinetic analysis of the interactions of complement receptor 2 (CR2, CD21) with its ligands C3d, iC3b, and the EBV glycoprotein gp350/220

J Immunol. 2001 Aug 1;167(3):1490-9. doi: 10.4049/jimmunol.167.3.1490.


The molecular mechanisms involved in the interaction of complement receptor 2 (CR2) with its natural ligands iC3b and C3d are still not well understood. In addition, studies regarding the binding site(s) of the receptor on C3 as well as the affinities of the C3 fragments for CR2 have produced contradictory results. In the present study, we have used surface plasmon resonance technology to study the interaction of CR2 with its ligands C3d, iC3b, and the EBV surface glycoprotein gp350/220. We measured the kinetics of binding of the receptor to its ligands, examined the influence of ionic contacts on these interactions, and assessed whether immobilized and soluble iC3b bound with similar kinetics to CR2. Our results indicate that 1) gp350 binding to CR2 follows a simple 1:1 interaction, whereas that of the C3 fragments is more complex and involves more than one intramolecular component; 2) kinetic differences exist between the binding of C3d and iC3b to CR2, which may be due to an additional binding site found on the C3c region of iC3b; and 3) iC3b binds to CR2 with different kinetics, depending on whether the iC3b is in solution or immobilized on the surface. These findings suggest that binding of CR2 to iC3b and C3d is more complex than previously thought.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / metabolism
  • Amino Acid Sequence
  • Baculoviridae / genetics
  • Biotinylation
  • Buffers
  • Complement C3b / metabolism*
  • Complement C3c / metabolism
  • Complement C3d / metabolism*
  • Herpesvirus 4, Human / genetics
  • Herpesvirus 4, Human / immunology
  • Herpesvirus 4, Human / metabolism*
  • Humans
  • Kinetics
  • Ligands
  • Lysine / metabolism
  • Molecular Sequence Data
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / metabolism
  • Protein Binding
  • Receptors, Complement 3d / genetics
  • Receptors, Complement 3d / metabolism*
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / isolation & purification
  • Sodium Chloride / metabolism
  • Surface Plasmon Resonance
  • Viral Matrix Proteins / genetics
  • Viral Matrix Proteins / metabolism*


  • Buffers
  • EBV-associated membrane antigen, Epstein-Barr virus
  • Ligands
  • Peptide Fragments
  • Receptors, Complement 3d
  • Recombinant Proteins
  • Viral Matrix Proteins
  • Sodium Chloride
  • Complement C3b
  • Complement C3c
  • Complement C3d
  • Lysine
  • Alanine