Purification of a novel DBI processing product, DBI39-75, and characterization of its binding site in rat brain.
This report describes the purification and characterization from rat brain of DBI39-75, a novel, biologically active processing product of diazepam binding inhibitor (DBI). We have shown that DBI39-75 in nM concentrations stimulates pregnenolone synthesis in mitochondria of rat brain. Using cross-linking of 125I-DBI39-75 in steroidogenically active concentrations we have demonstrated for the first time that the DBI fragment has a specific high affinity binding site in rat brain. Displacement of [3H]PK 11195 and [3H]Ro5-4864 by DBI39-75 indicates more complex interaction than the competitive inhibition. Collectively, the data suggest that the function of DBI39-75 is mediated through a mitochondrial receptor complex which includes binding sites for PK 11195 and Ro5-4864.
Slobodyansky
E
E
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20007.
Antkiewicz-Michaluk
L
L
Martin
B
B
D000595:Amino Acid Sequence; D000818:Animals; D001570:Benzodiazepinones / Q000378:metabolism*; D001665:Binding Sites; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents; D026261:Diazepam Binding Inhibitor; D007546:Isoquinolines / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology; D010446:Peptide Fragments / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology; D011284:Pregnenolone / Q000096:biosynthesis; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley
D001570:Benzodiazepinones; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D026261:Diazepam Binding Inhibitor; D007546:Isoquinolines; D009479:Neuropeptides; D010446:Peptide Fragments; C086753:diazepam binding inhibitor (39-75); C028513:4'-chlorodiazepam; D011284:Pregnenolone; C037850:PK 11195