Structural Role of Extracellular Domain 1 of α-Platelet-derived Growth Factor (PDGF) Receptor for PDGF-AA and PDGF-BB Binding

Daruka Mahadevan, Jin-Chen Yu, Jose W. Saldanha, Narmada Thanki, Peter McPhie, Aykut Uren, William J. LaRochelle, Mohammad A. Heidaran
1995 Journal of Biological Chemistry  
The purpose of this study was to bacterially express, purify, and refold combinations of the extracellular immunoglobulin (Ig)-like domains (2-3, 1-3, and 1-5) of the human ␣-platelet-derived growth factor receptor (␣PDGFR) to characterize molecular interactions with its ligand, platelet-derived growth factor (PDGF). The far UV circular dichroism spectroscopy of the ␣-PDGFR extracellular domains (ECDs) revealed a predominantly ␤-sheet protein, with a structure consistent with folded Ig-like
more » ... ins. The addition of PDGF-BB to these ECD types changed the conformation of all three types with a decrease in mean residue ellipticity in the following rank order: 1-5 ‫؍‬ 1-3 > 2-3. In striking contrast, addition of PDGF-AA to these ECD types markedly changed the conformation of ECD 2-3, by an increased mean residue ellipticity but no changes were observed for ECDs 1-3 and 1-5. PDGF-AA bound to the immobilized ECD types 2-3, 1-3, and 1-5 at concentrations of 20, 11, and 7.5 nM, respectively. In contrast, PDGF-BB bound the ECD types 2-3, 1-3, and 1-5 at concentrations of 3, 3, and 2.2 nM, respectively. Scatchard analysis of binding studies using labeled ECDs indicated that PDGF-BB bound ECD 1-3 and ECD 2-3 with K D values of 74 and 72 nM, respectively. While, PDGF-AA bound ECD 1-3 and ECD 2-3 with K D values of 33 and 87 nM, respectively. Therefore, our results indicated that the loss of ECD 1 impaired the binding affinity of ␣PDGFR ECD 1-3 toward PDGF-AA without having a similar effect on PDGF-BB binding. Together all of our data suggest that ECD 1 is differentially required for proper orientation of PDGF-AA but not PDGF-BB binding determinant within ECDs 2 and 3.
doi:10.1074/jbc.270.46.27595 pmid:7499222 fatcat:3it2jepv3bhmpcw7avjltcfc6q