FAQ: Which residues at the C-terminus of the target protein may inhibit cleavage or cause in vivo cleavage when the pTXB vectors are used?

Based on mutagenesis studies using paramyosin as the target protein, Ser, Pro or Asp at the -1 position (the amino acid preceding the intein) blocks the cleavage When the C-terminus of a target protein contains an unfavorable residue, additional residue(s) such as Tyr (the native residue preceding the Mxe GyrA intein), may be inserted between the target protein and the N-terminus of the intein to improve controlled cleavage. However, the cleavage efficiency may vary when a different target protein is fused to the intein.