title: Insulin-like growth factor binding proteins-3 and -5 form sodium dodecyl sulfate-stable multimers.
abstract: Insulin-like growth factor binding proteins (IGFBPs) are important modulators of IGF actions. IGFBP-3 and IGFBP-5 can bind to the extracellular matrix of a number of cell types. We now describe a new posttranslational structural modification of IGFBP-3 and IGFBP-5, which could play a role in determining their localization. We incubated radioiodinated forms of all six IGFBPs in the presence of a redox buffer consisting of 10 mM reduced glutathione and 0.2 mM oxidized glutathione. Under these conditions IGFBP-3 and IGFBP-5, but not the other IGFBPs, formed high molecular weight disulfide-linked multimers. Heparin and a peptide encompassing the high-affinity heparin-binding site in the C-terminal portion of IGFBP-3 were capable of blocking the multimerization of IGFBP-3. IGFBP-3, but not IGFBP-1, was shown to be able to self-associate non-covalently, which could be a requisite first step in the formation of covalent multimers. The self-association of IGFBP-3 required the high-affinity heparin-binding site in the C-terminal portion of the molecule.
authors.affiliation: Department of Paediatrics, Wilhelmina Children's Hospital, Utrecht University, The Netherlands. j.koedam@wkz.azu.nl
authors.forename: J A
authors.initials: JA
authors.lastname: Koedam
authors.forename: C M
authors.initials: CM
authors.lastname: Hoogerbrugge
authors.forename: S C
authors.initials: SC
authors.lastname: Van Buul-Offers
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005978:Glutathione / Q000494:pharmacology; D019803:Glutathione Disulfide / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000737:chemistry* / Q000378:metabolism; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000737:chemistry* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000032:analysis / Q000378:metabolism; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000494:pharmacology; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology*
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D007457:Iodine Radioisotopes; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012967:Sodium Dodecyl Sulfate; D007334:Insulin-Like Growth Factor I; D006493:Heparin; D005978:Glutathione; D019803:Glutathione Disulfide