Alternative Splicing Determines the Binding of Platelet-Derived Growth Factor (PDGF-AA) to Glycosaminoglycans†

摘要: We have shown previously that the platelet-derived growth factor (PDGF) and a synthetic oligopeptide, corresponding to basic carboxyl-terminal amino acid extension of long PDGF-A isoform, bind heparin. Here, we expressed (rA125) short (rA109) variants PDGF A-chains in Escherichia coli produced functional homodimers. Surface plasmon resonance analyses showed while dimeric rA125 bound with high affinity low molecular weight heparin, rA109, lacking extension, did not. This strongly indicated binding is due extension. Investigations kinetics thermodynamics suggested an allosteric mechanism. Thus, contains two equivalent sites. Following heparin one site, dimer undergoes conformational change, increasing for about 40 times. positive cooperativity requires both monomers molecule. Thermodynamics reaction, showing entropy-driven endothermic process, suggest involvement hydrophobic interactions this rearrangement. Three acids were essential interaction: residues Arg111 Lys116, polar Thr125. also found other glycosaminoglycan species, those by human arterial smooth muscle cells, heparan sulfate highest affinity.