Purification and characterization of a gamma-melanotropin precursor from frozen human pituitary glands.
A new melanocyte-stimulating peptide has been isolated from acid extracts of frozen human pituitary glands by salt/ethanol fractionation, Sephadex G-75 gel filtration and DEAE- and cM-cellulose ion-exchange chromatography. The peptide is glycosylated, has an N-terminal tryptophan residue and an apparent mol.wt. of 16000 as estimated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Its amino acid analysis closely resembles residues Trp-105 to Gln-29 predicted for the common precursor protein of bovine corticotropin and beta-lipotropin by Nakanishi, Inoue, Kita, Nakamura, Chang, Cohen & Numa [(1979) Nature (London) 278, 423-427]. This fragment is expected to have melanotropin activity due to the tetrapeptide -His-Phe-Arg-Trp- (residues -51 to -48) of the predicted sequence of the common precursor. It was found to have a molar potency of 1 X 10(-5) relative to alpha-melanotropin in the frog skin bioassay. These characteristics are consistent with the isolated melanotropin peptide being a non-corticotropin, non-lipotropin peptide of the human common precursor protein of corticotropin and lipotropin. The peptide neither potentiates the adrenal weight-maintenance activity of corticotropin-(1-24)-tetracosapeptide when administered to hypophysectomized rats, nor stimulates release of non-esterified fatty acids from isolated rat epididymal cells. A second N-terminal-tryptophan glycopeptide was also isolated, which had an amino-acid composition similar to that predicted for the bovine common precursor protein, residues Trp-105 to Gly-35.
D000596:Amino Acids / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D005615:Freezing; D006801:Humans; D009074:Melanocyte-Stimulating Hormones / Q000302:isolation & purification* / Q000494:pharmacology; D008544:Melanocytes / Q000187:drug effects; D010455:Peptides / Q000032:analysis; D010902:Pituitary Gland / Q000032:analysis*
D000596:Amino Acids; D002241:Carbohydrates; D010455:Peptides; D009074:Melanocyte-Stimulating Hormones