VEGF R2 (mouseFlk1 gene), VEGF R1 (Flt1) and VEGF R3 (Flt4) belong to the class III subfamily of receptor tyrosine kinases (RTKs). All three receptors contain seven immunoglobulinlike repeats in their extracellular domains and kinase insert domains in their intracellular regions. The expression of VEGF R1, 2, and 3 is almost exclusively restricted to the endothelial cells. These receptors are likely to play essential roles in vasculogenesis and angiogenesis. Mouse VEGF R2 cDNA encodes a 1367 amino acid (aa) precursor protein with a 19 aa signal peptide. Mature VEGF R2 is composed of a 743 aa extracellular domain, a 22 aa transmembrane domain, and a 583 aa cytoplasmic domain. In contrast to VEGF R1 which binds both PlGF and VEGF with high affinity, VEGF R2 binds VEGF but not PlGF with high affinity. The solube receptor was used as a an antigen.
