The application of an improved solid phase synthetic technique to the delineation of an antigenic site of apolipoprotein A-II.
Previous studies have shown that the antigenic sites of human plasma high-density apolipoprotein A-II (apoA-II) are separate from their lipid-binding determinants in human high density lipoproteins (HDL). A specific radioimmunoassay has shown that three distinct antigenic sites are located in residues 4-23, 31-46, and 56-77; these studies suggested that an antigenic site might be restricted to residues 60-77 in the 56-77 fragment. To further delineate this site, we have developed a solid phase radioimmunoassay technique using an improved solid support on which selected sequences of peptides were synthesized, deprotected with HF, and the resulting peptidyl-resins tested for their capability of binding purified 125I-anti-apoA-II antibodies. Amino acid analyses and solid phase sequence analyses were performed to verify the sequence of the synthetic peptide on the solid support. Using this technique, 125I-anti-apoA-II antibodies had achieved 50% of maximal binding when residues 61-77 were attached to the solid support. The maximal binding was achieved by the addition of one more residue, Leu60, thus confirming our suggestion that a major antigenic site is located in residues 60-77. The binding to the peptidyl-resin was inhibited by a synthetic fragment corresponding to residues 60-77 indicating that the antibodies were specifically bound to the resin.
D000595:Amino Acid Sequence; D000906:Antibodies / Q000302:isolation & purification; D016633:Apolipoprotein A-II; D001053:Apolipoproteins / Q000138:chemical synthesis / Q000276:immunology*; D001665:Binding Sites; D000939:Epitopes; D006801:Humans; D007120:Immunochemistry; D010446:Peptide Fragments / Q000138:chemical synthesis; D011863:Radioimmunoassay / Q000379:methods*
D000906:Antibodies; D016633:Apolipoprotein A-II; D001053:Apolipoproteins; D000939:Epitopes; D010446:Peptide Fragments