title: Steroidogenesis-activator polypeptide isolated from a rat Leydig cell tumor.
abstract: A cycloheximide-sensitive protein responsive to adenosine 3',5'-monophosphate has been postulated to participate in the regulation of cholesterol side-chain cleavage activity in steroidogenic tissues. Such a steroidogenesis activator polypeptide (SAP) had been isolated from rat adrenocortical tissue and partially characterized. Now a polypeptide with comparable chromatographic behavior and biological activity has been purified from the rat H-540 Leydig cell tumor in quantities sufficient for amino acid sequencing. The activator contains 30 amino acid residues and has a molecular weight of 3215. The synthetic construct based on this sequence is virtually equipotent with native H-540 tumor SAP in an adrenal mitochondrial cholesterol side-chain cleavage assay. Hormonal regulation of the intracellular concentration of this activator may control the rate of cholesterol metabolism in steroidogenic organs.
mesh_terms: D000302:Adrenal Cortex / Q000032:analysis; D000595:Amino Acid Sequence; D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D006360:Heat-Shock Proteins; D007984:Leydig Cell Tumor / Q000032:analysis*; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D018832:Molecular Chaperones; D010088:Oxidoreductases / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D011506:Proteins / Q000032:analysis*; D051381:Rats; D013256:Steroids / Q000096:biosynthesis*; D000091342:Endoplasmic Reticulum Chaperone BiP
chemical_list: D002784:Cholesterol; D002786:Cholesterol Side-Chain Cleavage Enzyme; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010088:Oxidoreductases; D010446:Peptide Fragments; D011506:Proteins; D013256:Steroids; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP