title: Functional importance of amino acid residues making up peptide antigenic determinants.
abstract: The functional importance of each amino acid residue making up the antigenic determinants of three different peptide-mAb interactions was determined using complete series of substitution analogs of the three immunizing synthetic peptides. Fingerprint substitution profiles for the three different antigenic determinants were obtained separately by direct and competitive ELISA. Competitive ELISA was found to offer the advantage of being able to measure the concn of each peptide substitution analog necessary to inhibit antibody binding to the original peptide. In this manner, the relative functional contribution to antibody binding of each amino acid residue making up the antigenic determinant was determined and termed the relative positional importance factor (RPIF). Each antigenic determinant was found to contain one very highly specific residue (i.e., highest RPIF) that was, on average, the least replaceable with any of the natural L-amino acids (the average decrease in recognition ranged 250- to 28,000-fold). At the other extreme, two or three positions in each antigenic determinant were found to be only weakly involved in recognition. These positions were considered redundant since the average decrease in recognition of the substitution analogs for these positions was found to be 20-fold or less. The remaining antigenic determinant residues exhibited the fine specificity common to antigen-antibody interactions in that only relatively conservative substitutions for these residues were recognized by their respective antibodies. It is of interest that the positional arrangement of specific and nonspecific residues were different for each of the three antigenic determinants examined.
authors.affiliation: Torrey Pines Institute for Molecular Studies, San Diego, CA 92121.
authors.forename: C
authors.initials: C
authors.lastname: Pinilla
authors.forename: J R
authors.initials: JR
authors.lastname: Appel
authors.forename: R A
authors.initials: RA
authors.lastname: Houghten
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D001667:Binding, Competitive; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D015681:Fusion Proteins, gag-onc / Q000737:chemistry / Q000276:immunology*; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral / Q000737:chemistry / Q000276:immunology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000276:immunology; D051153:Wnt Proteins; D029961:Zebrafish Proteins
chemical_list: D000596:Amino Acids; D000911:Antibodies, Monoclonal; D000939:Epitopes; D015681:Fusion Proteins, gag-onc; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D014759:Viral Envelope Proteins; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D011505:Protein-Tyrosine Kinases