Patent ID: 6881718

Claim:
A method of making a cell toxin comprisng reacting a polypeptide comprising a Pseudomonas exotoxin translocation domain linked to a Pseudomonas exotoxin ADP-ribosylatin domain, wherein the Pseudomonas exotoxin translocation domain comprises at least one reactive sulfhydryl group, with a substance P peptide comprising one additional cysteine residue at its amino terminal end, wherein the cysteine sulfhydryl group is disulfide linked to a di-thiobis (2-nitro)-benzoic acid group, such that after the reaction a disulfide bond is formed between the exotoxin polypeptide and the substance P and a thionitrobenzoate group is released, and purifying the substance P- Pseudomonas exotoxin disulfide linked conjugate from the released thionitrobenzoate group such that the purified conjugate is substantially free of thionitrobenzoate groups.