title: Human bone morphogenetic protein 2 contains a heparin-binding site which modifies its biological activity.
abstract: Bone morphogenetic protein 2 (BMP-2) plays a decisive role during bone regeneration and repair as well as during various stages of embryonal development. A cDNA encoding mature human BMP-2 could be efficiently expressed in Escherichia coli, and after renaturation a dimeric BMP-2 protein of M(r) 26,000 was prepared with a purity greater 98%. The recombinant BMP-2 was functionally active as demonstrated by the induction of alkaline phosphatase activity in the C3H10T1/2 fibroblast cell line (EC50 of 70 nM) and proteoglycan synthesis in embryonic chicken limb bud cells (EC50 of 15-20 nM). A peptide 1-17 representing the N-terminal basic part of BMP-2 as well as heparin increased the specific activity of the protein about fivefold in the limb bud assay. These observations suggested that the N-terminai reduce the specific activity of BMP-2, probably by interacting with heparinic sites in the extracellular matrix. This conclusion was supported by a variant EHBMP-2, where the N-terminal residues 1-12 of BMP-2 had been substituted by a dummy sequence of equal length and which showed an EC50 value of around 1 nM which was affected neither by heparin nor by peptide 1-17. A physical interaction between BMP-2 and heparin could be seen in biosensor experiments, where BMP-2 bound to immobilized heparin with a dissociation constant, Kd, of approximately 20 nM, whereas the heparin-binding of variant EHBMP-2 was negligible. These results identify the basic N-terminal domains of dimeric BMP-2 as heparin-binding sites that are not obligatory for receptor activation but modulate its biological activity.
authors.affiliation: Theodor-Boveri-Institut für Biowissenschaften (Biozentrum) Universität Würzburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Ruppert
authors.forename: E
authors.initials: E
authors.lastname: Hoffmann
authors.forename: W
authors.initials: W
authors.lastname: Sebald
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019485:Bone Morphogenetic Proteins; D002460:Cell Line; D018076:DNA, Complementary; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D019485:Bone Morphogenetic Proteins; D018076:DNA, Complementary; D011506:Proteins; D011994:Recombinant Proteins; D006493:Heparin