Residues contributing to substrate binding.

<p>Model of mature FheCL3 showing the S₂ and S₃ subsites of the active site: the His61 and Trp67 residues that were mutated in the present study are highlighted as sticks. The E64 inhibitor complexed with human cathepsin K (1ATK) was superimposed to facilitate viewing the active site cleft. The image was generated wth SPDBviewer <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002269#pntd.0002269-Guex1" target="_blank">[33]</a> The residues constituting the active site S₂ and S₃ subsites of FheCL1 and FheCL3 are indicated below the molecular representation.