Molecular interactions. The binding interactions between VEGF, surface receptors, extracellular matrix and basement membranes. VEGF165 binds to VEGFR1, VEGFR2, and co-receptors NRP1 and NRP2. VEGF165 also binds to glycosaminoglycan (GAG) chains in the extracellular matrix and basement membranes. VEGF121 binds to VEGFR1 and VEGFR2, but is unable to bind to NRPs. The molecular interactions between the VEGF isoforms and NRP1 or NRP2 are identical, but are governed by different kinetic parameters. The anti-VEGF agent binds to both isoforms. The receptors and co-receptors are inserted and internalized at the cell surface.