Site specificity of a catalytic vasoactive intestinal peptide antibody. An inhibitory vasoactive intestinal peptide subsequence distant from the scissile peptide bond.
Ten fragments of vasoactive intestinal peptide (VIP) were tested for reactivity with a human catalytic autoantibody that cleaves full-length VIP(1-28) at the Gln16-Met17 peptide bond. A large COOH-terminal subsequence, VIP(15-28), was bound by the autoantibody with high affinity (Ki 1.25 nM), suggesting that it is the antibody binding epitope. VIP(22-28), a short subsequence distant from the scissile bond, inhibited the binding (Ki 242 microM) and hydrolysis (Ki 260 microM) of full-length VIP by the catalytic autoantibody in a competitive fashion. The autoantibody did not show detectable binding of short VIP subsequences that encompass the scissile bond (VIP(15-21), VIP(11-17), and VIP(13-20]. These data show that residues 22-28, located four amino acids distant from the scissile bond, contribute in recognition of VIP by the catalytic autoantibody.
Paul
S
S
Department of Pharmacology, University of Nebraska Medical Center, Omaha 68105.
Volle
D J
DJ
Powell
M J
MJ
Massey
R J
RJ
D000595:Amino Acid Sequence; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001667:Binding, Competitive; D006801:Humans; D006868:Hydrolysis; D007074:Immunoglobulin G; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000276:immunology; D010455:Peptides / Q000138:chemical synthesis; D014660:Vasoactive Intestinal Peptide / Q000276:immunology* / Q000378:metabolism
D001323:Autoantibodies; D007074:Immunoglobulin G; D010446:Peptide Fragments; D010455:Peptides; D014660:Vasoactive Intestinal Peptide