VASCULAR ENDOTHELIAL GROWTH-FACTOR - CRYSTAL-STRUCTURE AND FUNCTIONALMAPPING OF THE KINASE DOMAIN RECEPTOR-BINDING SITE

Vascular endothelial growth factor (VEGF) is a homodimeric member of t he cystine knot family of growth factors, with limited sequence homolo gy to platelet-derived growth factor (PDGF) and transforming growth fa ctor beta 2 (TGF-beta). We have determined its crystal structure at a resolution of 2.5 Angstrom, and identified its kinase domain receptor (KDR) binding site using mutational analysis. Overall, the VEGF monome r resembles that of PDGF, but its N-terminal segment is helical rather than extended. The dimerization mode of VEGF is similar to that of PD GF and very different from that of TGF-beta. Mutational analysis of VE GF reveals that symmetrical binding sites for KDR are located at each pole of the VEGF homodimer. Each site contains two functional ''hot sp ots'' composed of binding determinants presented across the subunit in terface. The two most important determinants are located within the la rgest hot spot on a short, three-stranded sheet that is conserved in P DGF and TGF-beta. Functional analysis of the binding epitopes for two receptor-blocking antibodies reveal different binding determinants nea r each of the KDR binding hot spots.