Abstract

Four neurotoxic polypeptides (Tx2-1, Txt2-5, Tx2-6 and Tx2-9) were purified from the venom of the South American 'armed' spider Phoneutria nigriventer (Keys) by gel filtration and reverse phase FPLC and HPLC. These cysteine-rich polypeptides exhibited different levels of neurotoxicity in mice after intracerebroventricular injection. Tx2-1, Tx2-5 and Tx2-6 caused spastic paralysis and death, but the less toxic Tx2-9 produced only tail erection and scratching. The molecular weights of the polypeptides as determined by desorption mass spectroscoopy were 5838.8 for Tx2-1, 5116.6 (Tx2-5), 5291.3 (Tx2-6) and 3742.1 (Tx2-9). The complete amino acid sequences of the neurotoxins were determined by automated Edman degradation and by manual DABITC-PITC microsequence analysis of peptides obtained after digestions with various proteases. The amino acid sequences of Tx2-1 (53 residues), Tx2-5 (49 residues) and Tx2-6 (48 residues) were homologous, but had only limited similarities to the less toxic Tx2-9 (32 residues). All four polypeptides had varying sequence identities with other neurotoxins from different spider species and biologically active peptides from scorpions, a sea snail and seeds of Mirabilis jalapa.