Receptor binding profile of neuropeptide γ and its fragments: Comparison with the nonmammalian peptides carassin and ranakinin at three mammalian tachykinin receptors

Abstract

The tachykinin binding site preferences of neuropeptide γ (NPγ), its C- terminal fragments AcNPγ(3–21), AcNPγ(5–21), AcNPγ(7–21), and AcNPγ(9–21), other mammalian tachykinins, and the nonmammalian tachykinins ranakinin and carassin were examined in membrane binding competition studies. [ 125I]-Bolton-Hunter [Sar 9,Met(O 2) 11]SP (BHSarSP), [ 125I]-neurokinin A (INKA) and [ 125I]-Bolton-Hunter scyliorhinin II (BHScyII) were used to investigate NK-1, NK-2, and NK-3 sites, in rat submandibular gland, gastric fundus, and brain, respectively. Elongation of the neurokinin A molecule does not appear to influence binding to rat tachykinin NK-1 and NK-2 binding sites. Ranakinin has affinity for the NK-1 and NK-2 site similar to that of substance P and neurokinin A, respectively, but has low affinity for the NK-3 site. Despite its structural similarities to neuropeptide γ, carassin has only moderate affinity for rat tachykinin binding sites. Possession of an acidic residue at position 4 appears critical for binding to rat NK-2 sites.