title: Apparent molecular weight of substance P/neurokinin-1 receptors determined using a photoaffinity labelled probe, [(3'-125I) D-Tyro, (4'-N3)Phe8, Nle11]-substance P.
abstract: A photoreactive derivative, [(3'-125I) D-Tyro, (4'-N3)Phe8, Nle11]-substance P (SP) was prepared and iodinated using carrier-free [125I] to determine the apparent molecular weight of one sub-type of neurokinin (NK) receptor, the SP/NK-1 type. The unlabelled analogue competed for [3H]-SP sites with an IC50 of 10 nM. The radioactive photoprobe (KD approximately 0.17 nM, Bmax = 15.6 fmol/mg protein) was used to photoaffinity label membranes prepared from rat brain. Autoradiographs revealed that a single band with an apparent molecular weight of 46,000 daltons was specifically labelled. This labelling was inhibited by non-radioactive SP in a concentration-dependent manner (1.0 nM-0.1 mM) suggesting that the observed labelling represents the SP/NK-1 receptor type.
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001921:Brain / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007457:Iodine Radioisotopes; D008297:Male; D008970:Molecular Weight; D010777:Photochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D018040:Receptors, Neurokinin-1; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013373:Substance P / Q000031:analogs & derivatives* / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D007457:Iodine Radioisotopes; D018040:Receptors, Neurokinin-1; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter; C054297:substance P, Tyr(0)-(4'-N3)Phe(8)-Nle(11)-; D013373:Substance P