Fig. 3.

The alignment of the open reading frames of the Venus flytrap cysteine proteases with papain. The encircled area represents a conserved motif that is essential for the conversion from zymogen to the mature protease in papain and cathepsin L. The upward-pointing arrow (↑) indicates the cleavage site between the activation peptide and the mature protease in papain, and the downward-pointing arrow (↓) indicates the cleavage site between the activation peptide and the mature protease in dionain-1. The asterisks (*) represent the active site residues in papain, and the carets (∧) represent the cysteine residues involved in the disulfide bridges. The alignment strongly suggests that the active site residues and disulfide bridges are conserved between the five different plant cysteine proteases.