Takahiro Seki, Masabumi Minami, Chiaki Kimura, Tomoya Uehara, Takayuki
Nakagawa and Masamichi Satoh (*)
Department of Molecular Pharmacology, Faculty of Pharmaceutical Sciences,
Kyoto University, Kyoto 606-8501, Japan
(*) To whom correspondence should be addressed.
Abstract: We investigated the molecular basis of the discrimination
between nociceptin/orphanin FQ receptor (NociR) and opioid receptors (OPRs)
by bremazocine, a non-type-selective opioid ligand. Construction of several
chimeric receptors between NociR and kappa-opioid receptor (KOPR) and mutant
NociRs followed by binding experiments with [3H]bremazocine showed
that the mutation of only four amino acid residues of NociR, Ala216,
Val279, Gln280 and Val281, to the amino
acid residues located at the corresponding position of KOPR, Lys227,
Ile290, His291 and Ile292, made it possible
for the resultant mutant NociR to bind bremazocine with high affinity. Considering
that these four amino acid residues are conserved among mu-, delta- and
kappa-OPRs, the present result suggests that bremazocine recognizes the
difference in these four amino acid residues to discriminate between NociR
and OPRs.
Keywords: Nociceptin/orphanin FQ receptor, Opioid receptor, Bremazocine,
Chimeric receptor, Site-directed mutagenesis