title: Identification of a mammalian growth factor as a ribofolate peptide.
abstract: Thymocyte growth peptide (TGP) promotes DNA synthesis of immature thymocytes. TGP has been purified from sheep, human and calf thymus and recently characterized as an N-terminally blocked nonapeptide. Evidence is presented here that the blocking moiety consists of a formylpteroyl group bound to the N-terminal glutamyl residue of the nonapeptide. The pterin part of the TGP molecule has a ribityl substituent in analogy with riboflavin, which explains the pronounced hydrophilic property of TGP in contrast to unsubstituted and unconjugated folates. The compound can be classified as a ribofolate peptide, a novel class of growth factor. Zn2+ counteracts degradation of the molecule and is required for full biological activity; mass spectrometric data confirm that native TGP contains zinc.
authors.affiliation: Department of Histology and Neurobiology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Ernström
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002850:Chromatography, Gel; D004247:DNA / Q000096:biosynthesis; D005492:Folic Acid / Q000737:chemistry; D005971:Glutamates / Q000032:analysis* / Q000378:metabolism; D006133:Growth Substances / Q000737:chemistry* / Q000302:isolation & purification; D036341:Intercellular Signaling Peptides and Proteins; D002955:Leucovorin / Q000737:chemistry; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010455:Peptides / Q000737:chemistry* / Q000302:isolation & purification; D012756:Sheep; D013601:T-Lymphocytes / Q000378:metabolism*; D013950:Thymus Gland / Q000737:chemistry* / Q000166:cytology; D015032:Zinc / Q000737:chemistry
chemical_list: D005971:Glutamates; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C052275:thymocyte growth peptide; D004247:DNA; D005492:Folic Acid; C011398:4-aminobenzoylglutamic acid; D015032:Zinc; D002955:Leucovorin