CD309 is an alias for the gene, Kinase insert domain receptor, in humans. Other names include: Vascular endothelial growth factor receptor 2; VEGFR-2; Fetal liver kinase 1; FLK-1; Protein-tyrosine kinase receptor flk-1; CD antigen CD309; FLK1; VEGFR; VEGFR2. The encoded protein is an enzyme with an amino acid length of 1356 and a mass of 151.5 kDa. CD309 is a member of the Protein kinase superfamily, Tyr protein kinase family, CSF-1/PDGF receptor subfamily. This gene shares homology with other species, including: Mouse, Rat, Arabidopsis, Zebrafish, Frog, Chicken.