Primary structure and receptor-binding properties of a neurokinin A-related peptide from frog gut.
A tachykinin peptide was isolated from an extract of the intestine of the European green frog, Rana ridibunda, and its primary structure was established as: His-Lys-Leu-Asp-Ser-Phe-Ile-Gly-Leu-Met.CONH2. This sequence was confirmed by chemical synthesis and shows two amino acid substitutions (leucine for threonine at position 3 and isoleucine for valine at position 7) compared with neurokinin A. Binding parameters for synthetic [Leu3,Ile7]neurokinin A and mammalian tachykinins were compared using receptor-selective radioligands and crude membranes from tissues enriched in the NK1, NK2 and NK3 receptors. [Leu3,Ile7]Neurokinin A was approx. 3-fold less potent than substance P in inhibiting the binding of 125I-labelled [Sar9,Met(O2)11]substance P (labelled with Bolton-Hunter reagent) to rat submandibular gland (NK1 receptor), 8-fold less potent than neurokinin A in inhibiting the binding of [2-[125I]iodohistidine1]neurokinin A to rat stomach fundus (NK2 receptor) and 6-fold less potent than neurokinin B in inhibiting the binding of 125I-Bolton-Hunter-labelled scyliorhinin II to rat brain (NK3 receptor). Thus the frog neurokinin A-related peptide shows moderate affinity but lack of selectivity for all three tachykinin-binding sites in rat tissues. This non-selectivity is similar to that displayed by the molluscan tachykinin, eledoisin, which also contains an isoleucine residue in the corresponding position in the molecule.
Wang
Y
Y
Department of Biomedical Sciences, Creighton University Medical School, Omaha, NE 68178.
Badgery-Parker
T
T
Lovas
S
S
Chartrel
N
N
Vaudry
H
H
Burcher
E
E
Conlon
J M
JM
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005260:Female; D007421:Intestine, Small / Q000737:chemistry*; D008969:Molecular Sequence Data; D015288:Neurokinin A / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D011895:Rana ridibunda; D051381:Rats; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015320:Tachykinins / Q000378:metabolism
D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter; D015320:Tachykinins; C077929:neurokinin A, Leu(3)-Ile(7)-; D015288:Neurokinin A