Human serum amyloid P component binds to a specific peptide in the presence of calcium.

Human serum amyloid P component (SAP) binds to a carboxyl-terminal peptide of residues 160-204 of SAP itself in the presence of calcium. A set of sequentially overlapping decapeptides covering the entire length of residues 160-204 of SAP was synthesized on polyethylene pins to be used for binding assay, and six overlapping peptides in residues 190-204 (Tyr-Glu-Ile-Arg-Gly-Tyr-Val-Ile-Ile-Lys-Pro-Leu-Val-Trp-Val) were found to have equally high affinity for SAP. The validity of using peptides on polyethylene pins was shown by the binding assay using 11-residue soluble peptide corresponding to residues 194-204. Replacement of the Lys or the Ile residues with Glu abolished the binding activity.