Binding and immunological properties of a synthetic peptide corresponding to the phosphorylcholine-binding region of C-reactive protein.

A synthetic peptide corresponding to amino acid residues 47-63 of human C-reactive protein (CRP) was synthesized and evaluated for its ability to bind phosphorylcholine (PC) and to react with mAb specific for the PC-binding region of CRP. The PC-binding peptide displayed Ca2(+)-independent binding specific for PC and was able to compete against CRP for PC in the presence of Ca2+ ions. The synthetic peptide, like CRP, binds to the extracellular matrix protein fibronectin and the basement membrane protein laminin. The PC-binding peptide was recognized by those mAb generated against the intact CRP molecule that bind at, or near, the functional PC-binding region. In addition, several mAb to the T-15 idiotype present on mouse antibodies specific for PC, recognize an epitope(s) on the PC-binding peptide. Therefore, the 17 amino acid synthetic peptide shares both functional binding activity and antigenicity with the corresponding functional region within the CRP molecule.