Amino acid sequence of SpTx-1. The partial sequence of the purified inhibitor obtained from Edman degradation (A; each letter X indicates an ambiguous residue type that was subsequently determined to be the corresponding one shown in B), the full sequence deduced from cDNA sequencing (B), and the sequence with an extra N-terminal segment containing a 6-His-tag followed by a spacer sequence and then by the cleaving site of the protease TEV (C), where the His-tag and the TEV-cleaving sequence were colored maroon and cyan, respectively.