title: Involvement of loop 2 of platelet-derived growth factor-AA and -BB in receptor binding.
abstract: Platelet-derived growth factor (PDGF) is a disulfide-bonded antiparallel dimer of A- and B-polypeptide chains. Each subunit contains two loops (loops 1 and 3) which point in the same direction, and which are located close to a region (loop 2) from the other subunit of the dimer. Previous studies have shown that epitopes in loops 1 and 3 are important for binding to PDGF alpha- and beta-receptors. The aim of the present investigation was to determine the importance of loop 2 for receptor interactions. PDGF A- and B-chain cDNA:s were mutated in the loop 2 regions and transfected into COS cells. Analyses of conditioned media of such cell cultures revealed that PDGF B-chain mutated in the loop 2 region lost its ability to compete with 125I-PDGF for binding to PDGF beta-receptors, but retained 2-5% of its binding of alpha-receptors. The A-chain binds only to alpha-receptors; 2-5% of this binding was also retained after mutation of the loop 2 region. In conclusion, the loop 2 region of PDGF is important for receptor binding, but appears to be more important for binding to the PDGF beta-receptors than to the alpha-receptors.
authors.affiliation: Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Andersson
authors.forename: A
authors.initials: A
authors.lastname: Ostman
authors.forename: J
authors.initials: J
authors.lastname: Kreysing
authors.forename: G
authors.initials: G
authors.lastname: Bäckström
authors.forename: M
authors.initials: M
authors.lastname: Van de Poll
authors.forename: C H
authors.initials: CH
authors.lastname: Heldin
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D017077:Culture Media, Conditioned; D004220:Disulfides / Q000378:metabolism; D016228:Endothelial Growth Factors / Q000737:chemistry; D006801:Humans; D008222:Lymphokines / Q000737:chemistry; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010982:Platelet-Derived Growth Factor / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D017077:Culture Media, Conditioned; D004220:Disulfides; D016228:Endothelial Growth Factors; D008222:Lymphokines; D046911:Macromolecular Substances; D010982:Platelet-Derived Growth Factor; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D017479:Receptors, Platelet-Derived Growth Factor