Activates the vascular endothelial growth factor receptor-1 (VEGFR-1/FLT1), and consequently promotes the proliferation and tissue factor production of endothelial cells, the neovascularization in the chicken chorioallantoic membrane, and increases vascular permeability. Also stimulates tissue-factor production and human monocyte chemotaxis. Homodimer; disulfide-linked (By similarity). Interacts with high affinity with VEGFR-1/FLT1, and with lower affinity with VEGFR-2/KDR. Does not bind to VEGFR-3/FLT4 and neuropilin-1 (NRP1). Expressed by the venom gland. Belongs to the PDGF/VEGF growth factor family. Snake venom VEGF subfamily.