Tx2-6 is a toxin found in the venom of the Brazilian wandering spider, Phoneutria nigriventer (Keys). It is a peptide of 48 residues, molecular weight 5291.3.[1] This peptide is cleaved from a longer precursor with a signal peptide and a glutamine-rich propeptide. It can cause priapism. Tests on rats indicate that the toxin causes nitric oxide release, and its effect on erection is blocked by the nitric oxide synthase inhibitor L-NAME. However, it fully restored erectile function in rats developing hypertension due to injection of deoxycorticosterone acetate.[2] A study is underway at the Medical College of Georgia looking at possible uses for the chemical in erectile dysfunction medication.[3]