The GABAA receptor family in the mammalian brain.
The GABAA-benzodiazepine receptor protein from bovine brain was purified by affinity chromatography and the subunit composition examined by gel electrophoresis in sodium dodecyl sulfate. Protein staining revealed a doublet at 51-53 kDa, a band at 55 kDa, and a broad band at 57-59 kDa. The 51 and 53 kDa bands co-migrated with the alpha 1 and alpha 2 gene products identified by Western blotting with subtype-specific antibodies. These two bands were also photoaffinity labeled by [3H]flunitrazepam, as was a breakdown product at 44 kDa. Partial sequencing of proteolytic fragments of these polypeptides yielded sequences found in all alpha clones, and identified the benzodiazepine binding site within residues 8-297 and probably between 106-297 of alpha 1; the 44 kDa and 31 kDa bands yielded fragments containing alpha 3 sequence. The native alpha 3 polypeptide was identified with subtype-specific antibody at 57 kDa overlapping with the two major bands photolabeled with [3H]muscimol at 55 and 58 kDa. Antisera to a beta-selective peptide recognized four bands at 60, 58, 57 and 55 kDa. Thus, one can identify 6-8 distinct polypeptides with the possibility of another 4-6 in purified GABAA receptor proteins, depending on brain region, consistent with the family of gene products suggested by molecular cloning.
Olsen
R W
RW
Department of Pharmacology, School of Medicine, University of California, Los Angeles 90024.
Bureau
M H
MH
Endo
S
S
Smith
G
G
D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001923:Brain Chemistry; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D005445:Flunitrazepam / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009118:Muscimol / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D010777:Photochemistry; D051381:Rats; D011963:Receptors, GABA-A / Q000737:chemistry* / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism
D000345:Affinity Labels; D010446:Peptide Fragments; D011963:Receptors, GABA-A; D009118:Muscimol; D005445:Flunitrazepam; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase