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Four neurotoxic polypptidcs were purified from the venom of the South American 'armed' spider Phuncmiu nigrivenrer (Keys) by gel filtration and rcvcrse phase FPLC and HPLC. These cystcine-rich polypcptidcs exhibited dimerent lcvcls of neurotoxicity in mice after intraccrebrovcntricular injection. Tic'-I, TxZ5 and Tx2-6 caused spastic paralysis nnd deuh, 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 (Txl-5). 5291.3 (Tx2-6) and 3742.1 (Tx2-9). The complele amino acid sequences of the neurotoxins were determhxd by automnted Edman degradation and by manual DABITC-PITC microscqeuncc analysis of peptidcs obtained atIer digestions with various proteases. The amino acid sequences ofTx2.1 (53 residue), 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 bad varying seqlxnce identities with other neurotoxins from different spider species and biologiiwlly active peptides from scorpions, a sea snail and seeds of Mirrrliitijufupa.Spider venom; Amino acid xquence; Neuroloxin; Phoneutriu rri~rivwkr

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