Identification of an epitope in the substance P receptor important for recognition of the common carboxyl-terminal tachykinin sequence.
The substance P receptor and the anti-substance P antibody NC1 share the ability to bind to the COOH terminus of substance P. Sequence analysis identified a direct noninterrupted homology of 5 residues in the two molecules. Replacement of Gly166 and Tyr167 in this epitope of the substance P receptor by the corresponding substance K receptor amino acids (Cys and Phe) increases the affinity toward substance P 2-fold and toward substance K and neurokinin B 11- and 21-fold, respectively. A significantly larger effect of the mutation is observed for the hexapeptides of substance P and substance K which show a mutation-induced increase in binding energy of more than 2 kcal/mol. Hence, the NH2 terminus of substance P and, to a lesser extent, of substance K masks the effect of the mutation. I conclude that the epitope is important for recognition of the common COOH terminus of the tachykinins and for preservation of selectivity. The data furthermore suggest that formation of the peptide-receptor complex occurs through a composite set of interactions which are not adequately described by the two-site/no cooperativity "address-message" model.
Werge
T M
TM
Consiglio Nazionale delle Ricerche Institute of Neurobiology, Rome, Italy.
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D001483:Base Sequence; D002478:Cells, Cultured; D000939:Epitopes / Q000378:metabolism*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D051381:Rats; D018040:Receptors, Neurokinin-1 / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*; D015320:Tachykinins / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D009838:Oligodeoxyribonucleotides; D018040:Receptors, Neurokinin-1; D015320:Tachykinins; D013373:Substance P