title: Structural investigations on a peptide regulating hemopoiesis in vitro and in vivo.
abstract: Clonal growth in agar of myeloid committed stem cells (CFU-c) is inhibited by a specifically acting "hemoregulatory peptide" which had been isolated from human leukocytes. The inhibitory peptide is composed of aspartic acid, glutamic acid, lysine, cysteine and possibly glycine. It was [3H]carboxymethylated with [3H]iodoacetic acid. From the electrophoretic behaviour of this derivative at pH 1.9 a single positive charge and a molecular mass of about 600-650 Da could be inferred. This positive charge is lost after acetylation and is identified as the epsilon-amino group in the side chain of a lysine residue since the N-terminal group is a pyroglutamic residue. Electrophoresis of the native peptide at pH 6.5 reveals the presence of three carboxyl groups, two of which were localized in the N-terminal part of the molecule, while cysteine and lysine were located in the C-terminal portion. Lysine was identified as the C-terminal residue by a double labeling technique applied to the Cys-[(3H]Cm)-containing fission peptide after partial hydrolysis. Uncertainties in the molecular mass determinations allow for the possible presence of a small residue without reactive side chain (glycine?) in the C-terminal portion of the molecule. The structure of the inhibitory peptide was thus determined as less than Glu-(Asp/Glu)-(Asp/Glu)-Cys-(Gly?)-Lys. This structure is supported by comparison with synthetic peptides. The analogue less than Glu-Glu-Asp-Cys-Lys has properties which are similar to those of the natural inhibitor.
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D002999:Clone Cells; D003619:Dansyl Compounds; D006410:Hematopoiesis / Q000187:drug effects*; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D007461:Iodoacetates; D019807:Iodoacetic Acid; D007962:Leukocytes / Q000502:physiology; D009842:Oligopeptides / Q000302:isolation & purification* / Q000494:pharmacology; D014316:Tritium; D014357:Trypsin
chemical_list: D002250:Carbon Radioisotopes; D003619:Dansyl Compounds; D007461:Iodoacetates; D009842:Oligopeptides; D014316:Tritium; D014357:Trypsin; C029038:dansyl chloride; D019807:Iodoacetic Acid