Figure 1: Falcipains have unique features. Falcipains are papain family cysteine proteases, active site residues (Cys, His, Asn) are conserved within the papain family, but falcipains have a unique N-terminal extension acting as a refolding domain, and a C-terminal insert as a hemoglobin (Hb) binding domain. Prodomain has ERFNIN and GNFD motifs, conserved in falcipains, papain, and cathepsin.