title: The bovine insulin-like growth factor (IGF) binding protein purified from conditioned medium requires the N-terminal tripeptide in IGF-1 for binding.
abstract: The insulin-like growth factor binding protein (BP) secreted by bovine kidney (MDBK) cells has been purified by affinity chromatography on a rat IGF-2 Sepharose column. Purified BP migrated as a single band of Mr 40,000 upon SDS polyacrylamide gel electrophoresis. An N-terminal sequence of 53 residues was obtained which was very similar up to residue 21 to the corresponding rat BRL-3A BP sequence. In competitive binding experiments with bovine IGF-1 and IGF-2, and recombinant human IGF-1, BP had a similar affinity for these ligand when IGF-1 tracer was used, but a higher affinity for IGF-2 with IGF-2 as radioligand. The N-terminal destripeptide truncated form of bovine IGF-1, which has enhanced biological activity, was found to have a markedly reduced affinity for BP compared to intact IGF-1. The increased bioactivity of destripeptide IGF-1 can be explained by this reduced affinity for BP.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D010449:Peptide Mapping; D010455:Peptides / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D003470:Culture Media; D018969:Insulin-Like Growth Factor Binding Proteins; D010455:Peptides; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II