title: The two NK-1 binding sites are distinguished by one radiolabelled substance P analogue.
abstract: Two non-stoichiometric binding sites had previously been characterized for the NK-1 receptor using two different types of radiolabelled analogues of substance P. However, the question remained on their eventual conformational interconversion induced or not by the ligand. In this study, kinetic, saturation, and competition studies using [3H]propionyl[Pro(9)]SP demonstrate the existence of two independent binding components in CHO cells transfected with the human NK-1 receptor, with K(d) values of 0.040 nM ( approximately 20% of total sites) and 5.9 nM ( approximately 80% of total sites) that correspond to those of the two previously described binding sites. These two binding sites do not seem to interconvert since the minor one can be selectively extinguished in saturation studies in the presence of a SP analogue specific of this binding site.
authors.affiliation: UMR 7613 Université Pierre et Marie Curie-CNRS, case courier 182, 4 place Jussieu, 75005 cedex, Paris, France.
authors.forename: Hyun Ryoung
authors.initials: HR
authors.lastname: Kim
authors.forename: Solange
authors.initials: S
authors.lastname: Lavielle
authors.forename: Sandrine
authors.initials: S
authors.lastname: Sagan
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011392:Proline / Q000737:chemistry / Q000378:metabolism; D011869:Radioligand Assay; D018040:Receptors, Neurokinin-1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013373:Substance P / Q000737:chemistry* / Q000378:metabolism; D014316:Tritium / Q000737:chemistry / Q000378:metabolism
chemical_list: D010455:Peptides; D018040:Receptors, Neurokinin-1; D014316:Tritium; D013373:Substance P; D011392:Proline