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The common C‐terminal sequences of substance P and neurokinin A contact the same region of the NK‐1 receptor
Author(s) -
Bremer Andrew A.,
Leeman Susan E.,
Boyd Norman D.
Publication year - 2000
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(00)02228-6
Subject(s) - neurokinin a , peptide , receptor , chemistry , stereochemistry , tachykinin receptor , binding site , peptide sequence , residue (chemistry) , substance p , photoaffinity labeling , biochemistry , amino acid , neuropeptide , gene
Although neurokinin A (NKA), a tachykinin peptide with sequence homology to substance P (SP), is a weak competitor of radiolabeled SP binding to the NK‐1 receptor (NK‐1R), more recent direct binding studies using radiolabeled NKA have demonstrated an unexpected high‐affinity interaction with this receptor. To document the site of interaction between NKA and the NK‐1R, we have used a photoreactive analogue of NKA containing p ‐benzoyl‐ L ‐phenylalanine (Bpa) substituted in position 7 of the peptide. Peptide mapping studies of the receptor photolabeled by 125 I‐iodohistidyl 1 ‐Bpa 7 NKA have established that the site of photoinsertion is located within a segment of the receptor extending from residues 178 to 190 (VVCMIEWPEHPNR). We have previously shown that 125 I‐BH‐Bpa 8 SP, a photoreactive analogue of SP, covalently attaches to M 181 within this same receptor sequence. Importantly, both of these peptides ( 125 I‐iodohistidyl 1 ‐Bpa 7 NKA and 125 I‐BH‐Bpa 8 SP) have the photoreactive amino acid in an equivalent position within the conserved tachykinin carboxyl‐terminal tail. In this report, we also show that site‐directed mutagenesis of M 181 to A 181 in the NK‐1R results in a complete loss of photolabeling of both peptides to this receptor site, indicating that the equivalent position of SP and NKA, when bound to the NK‐1R, contact the same residue.