Regulatory elements within the prodomain of Falcipain-2, a cysteine protease of the malaria parasite Plasmodium falciparum

PLoS One. 2009 May 27;4(5):e5694. doi: 10.1371/journal.pone.0005694.


Falcipain-2, a papain family cysteine protease of the malaria parasite Plasmodium falciparum, plays a key role in parasite hydrolysis of hemoglobin and is a potential chemotherapeutic target. As with many proteases, falcipain-2 is synthesized as a zymogen, and the prodomain inhibits activity of the mature enzyme. To investigate the mechanism of regulation of falcipain-2 by its prodomain, we expressed constructs encoding different portions of the prodomain and tested their ability to inhibit recombinant mature falcipain-2. We identified a C-terminal segment (Leu(155)-Asp(243)) of the prodomain, including two motifs (ERFNIN and GNFD) that are conserved in cathepsin L sub-family papain family proteases, as the mediator of prodomain inhibitory activity. Circular dichroism analysis showed that the prodomain including the C-terminal segment, but not constructs lacking this segment, was rich in secondary structure, suggesting that the segment plays a crucial role in protein folding. The falcipain-2 prodomain also efficiently inhibited other papain family proteases, including cathepsin K, cathepsin L, cathepsin B, and cruzain, but it did not inhibit cathepsin C or tested proteases of other classes. A structural model of pro-falcipain-2 was constructed by homology modeling based on crystallographic structures of mature falcipain-2, procathepsin K, procathepsin L, and procaricain, offering insights into the nature of the interaction between the prodomain and mature domain of falcipain-2 as well as into the broad specificity of inhibitory activity of the falcipain-2 prodomain.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Catalytic Domain
  • Cathepsin B / antagonists & inhibitors
  • Cathepsin B / chemistry
  • Cathepsin L
  • Cathepsins / antagonists & inhibitors
  • Cathepsins / chemistry
  • Circular Dichroism
  • Conserved Sequence
  • Cysteine Endopeptidases / chemistry*
  • Enzyme Stability
  • Malaria, Falciparum / enzymology*
  • Models, Molecular
  • Molecular Sequence Data
  • Parasites / enzymology*
  • Peptide Fragments / chemistry
  • Plasmodium falciparum / enzymology*
  • Protein Precursors / chemistry
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Structural Homology, Protein
  • Substrate Specificity


  • Peptide Fragments
  • Protein Precursors
  • Cathepsins
  • Cysteine Endopeptidases
  • falcipain 2
  • Cathepsin B
  • Cathepsin L