[3H]muscimol photolabels the gamma-aminobutyric acid receptor binding site on a peptide subunit distinct from that labeled with benzodiazepines.
Affinity column-purified GABA-benzodiazepine receptor protein from bovine brain was photoaffinity labeled with both [3H]flunitrazepam and [3H]muscimol. Gel electrophoresis in sodium dodecyl sulfate revealed that the benzodiazepine binding site labeled with [3H]flunitrazepam was primarily associated with a major peptide subunit revealed by protein staining with Mr = 52 kiloDaltons, with minor labeling of a second peptide of Mr = 57 kiloDaltons, corresponding to a second major stained band. Covalent incorporation of [3H]muscimol was limited to the 57 kiloDalton band, with no labeling of the 52 kiloDalton peptide, showing that the GABA binding site is carried by a subunit distinct from that carrying the benzodiazepine binding site.
D000345:Affinity Labels; D000818:Animals; D001569:Benzodiazepines / Q000378:metabolism*; D001665:Binding Sites; D002417:Cattle; D002540:Cerebral Cortex; D005445:Flunitrazepam / Q000378:metabolism; D066298:In Vitro Techniques; D009118:Muscimol / Q000378:metabolism*; D010777:Photochemistry; D011963:Receptors, GABA-A / Q000378:metabolism*; D013997:Time Factors; D014466:Ultraviolet Rays
D000345:Affinity Labels; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D009118:Muscimol; D005445:Flunitrazepam