Characterization of 2-[125I]iodomelatonin binding sites in the brain of a marsupial, Bennett's wallaby (Macropus rufogriseus rufogriseus).
1. Specific high affinity binding of 2-[125I]iodomelatonin was detected in the brain of the pouch young of a marsupial, Bennett's wallaby. 2. Binding was rapid, stable, saturable and reversible. 3. Scatchard analysis indicated a single class of high affinity binding sites with an equilibrium dissociation constant (Kd) of 68 +/- 13 pM, a maximal number of binding sites (Bmax) of 0.7 +/- 0.1 fmol/mg protein and a Hill coefficient (nH) of 1.12 +/- 0.10. 4. Specific binding was inhibited by GTP (1 mM) indicating that the melatonin receptor is coupled to a guanine nucleotide binding protein, and by melatonin and closely related analogues with a potency order identical to that reported previously in the brain of eutherian mammals, birds and a reptile. 5. These studies suggest that the melatonin receptor is well-conserved through evolution.
Institute of Zoology, London, U.K.
A
A
Paterson
N W
NW
Chong
B R
BR
Brinklow
A S
AS
Loudon
D
D
Sugden
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D005075:Biological Evolution; D001921:Brain / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D007700:Kinetics; D008394:Marsupialia / Q000378:metabolism*; D008550:Melatonin / Q000031:analogs & derivatives* / Q000378:metabolism; D014018:Tissue Distribution
C044556:2-iodomelatonin; D019204:GTP-Binding Proteins; D008550:Melatonin