title: Bufokinin: a substance P-related peptide from the gut of the toad, Bufo marinus with high binding affinity but low selectivity for mammalian tachykinin receptors.
abstract: A tachykinin peptide, termed bufokinin, was isolated in pure form from an extract of the intestine of the toad, Bufo marinus, and its primary structure was established as: Lys-Pro-Arg-Pro-Asp-Gln-Phe-Tyr-Gly-Leu-Met.NH2. This sequence was confirmed by chemical synthesis and shows four amino acid substitutions (Arg1 --> Lys,Lys3 --> Arg,Gln5 --> Asp and Phe8 --> Tyr) compared with substance P. Binding parameters for synthetic bufokinin and mammalian tachykinins were compared using receptor-selective radioligands and crude membranes from rat tissues enriched in the NK-1 (submandibular gland) , NK-2 (stomach fundus) and NK-3 (brain) receptors. In terms of inhibiting the binding of the selective radioligands, bufokinin (Kd = 0.3 nM) was 1.8-fold more potent than substance P at the rat NK-1 site, but it was only 2-fold less potent (Kd = 2.8 nM) than neurokinin A at the NK-2 site and only 2-fold less potent (Kd = 48 nM) than neurokinin B at the NK-3 site. Thus, bufokinin shows relatively high affinity but lack of selectivity for all three tachykinin binding sites in rat tissues.
authors.affiliation: Regulatory Peptide Center, Department of Biomedical Sciences, Creighton University Medical School, Omaha, Nebraska 68178-0405, USA. jmconlon@creighton.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Conlon
authors.forename: F J
authors.initials: FJ
authors.lastname: Warner
authors.forename: E
authors.initials: E
authors.lastname: Burcher
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002024:Bufo marinus; D002352:Carrier Proteins; D002851:Chromatography, High Pressure Liquid; D005260:Female; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D009842:Oligopeptides / Q000737:chemistry*; D051381:Rats; D018039:Receptors, Tachykinin / Q000378:metabolism*; D013373:Substance P / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009842:Oligopeptides; D018039:Receptors, Tachykinin; C112071:bufokinin; D013373:Substance P