Vascular endothelial Growth Factor Receptor 2 (VEGFR2), also known as FLK-1, KDR, and CD309, is a type I single-pass membrane receptor,and is one of the subtypes of VEGFR. VEGF receptors are receptors for vascular endothelial growth factor (VEGF). Mature VEGFR2 contains a 745 amino acid extracelluar domain with seven immunoglobulin-like repeats, 21 transmembrane domain and 571 cytoplasmic domain. Within the extracellular domain, human VEGFR2 shares 80% homology with that of mouse and rat. VEGFR-2 appears to mediate almost all of the known cellular responses to VEGF. In addition, VEGFR2 is able to interact with HIV-1 extracellular Tat protein upon VEGF activation, and seems to enhance angiogenesis in Kaposi's sarcoma lesions.