Blocks olfactory (CNGA2) and retinal (CNGA1) cyclic nucleotide-gated (CNG) ion channel currents. Does not inhibit retinal (CNGA3) currents. It forms high-affinity contacts with the pore turret region and most likely inhibits CNG channel current by blocking the external entrance to the transmembrane pore. Does not affect neither depolarization- nor caffeine-induced contraction arterial smooth muscle (By similarity). Expressed by the venom gland. Belongs to the CRISP family.