A rabbit antiserum raised against the hexapeptide endothelin(16-21) shows different binding affinities for endothelin-1, -2 and -3.
A antiserum raised against the C-terminal hexapeptide ET16-21 common to ET-1, -2 and -3 was produced and characterized with respect to its binding properties for ET-1, -2, -3, ET16-21, the C-terminal octapeptide ET14-21, its derivative Phe21-ET14-21 and human big-ET-1. The antibody reacted with the peptides with decreasing binding affinities in the order: ET-1 greater than ET-2 greater than or equal to ET16-21 = ET 14-21 much greater than Phe21-ET14-21. It showed no crossreactivity with human big-ET-1. Similar results were obtained using [125I]ET-1, -2 or -3 as tracer. Substitution of Trp21 by Phe decreased the binding affinity of ET14-21 about 10 fold. Thus, the immunologically recognized sequence of the peptides is C-terminal and Trp21 seems to be important for high binding affinities. The significant differences in binding affinity observed for ET-1, -2, -3 and ET16-21 are consistent with an interaction of the C-terminal part of the endothelins with the bicyclic N-terminal part.
Löffler
B M
BM
Pharma Division, F.Hoffmann-La Roche Ltd, Basel, Switzerland.
Jacot-Guillarmod
H
H
D000595:Amino Acid Sequence; D000818:Animals; D000915:Antibody Affinity; D003429:Cross Reactions; D019332:Endothelin-1; D016232:Endothelins / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D007106:Immune Sera / Q000276:immunology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology*; D011498:Protein Precursors / Q000737:chemistry / Q000276:immunology; D011817:Rabbits
D019332:Endothelin-1; D016232:Endothelins; D007106:Immune Sera; D010446:Peptide Fragments; D011498:Protein Precursors; C061533:endothelin (16-21)