The Crystal Structure of Cruzain: A Therapeutic Target for Chagas' Disease

doi:10.1006/jmbi.1994.0137

Journal of Molecular Biology

Volume 247, Issue 2, 24 March 1995, Pages 251-259

https://doi.org/10.1006/jmbi.1994.0137 Get rights and content

Abstract

Trypanosoma cruzia protozoan parasite, is the etiologic agent of American trypanosomiasis or Chagas' disease. Chagas' disease afflicts more than 24 million individuals in South and Central America producing a debilitating life-long disease. It is the leading cause of heart failure in many Latin American countries. Currently, there is no satisfactory treatment for this parasitic infection. Cruzain (also known as cruzipain, gp 57/51), the major cystine protease present inT. cruzi, is critical for the devlopment and survival of the parasite within the host cells, making this enzyme a target for potential trypanocidal drugs. Here we report the X-ray crystal structure of cruzain complexed with the potent inhibitor Z-Phe-Ala-fluoromethyl ketone. The structure was determined at 2.35 Å (R_cryst=0.15) by molecular replacement using a modified papain as the search model. The refined structure is compared to papain. Features which distinguish cruzain from papain are discussed since they may aid in the design of specificity inhibitors. Fluorescence microscopy shows that a biotinylated form of the bound inhibitor does not effectively reach host proteases in their lysosomal compartment, but is selectivly taken up by the parasite. The inhibitor greatly reduces parasitemia in a cell culture system, without adverse effects to mammalilan cells. This biological selectivity can be exploited, in conjuction with unique active site features revealed by the crystal structure, to develop chemotherapy for Chagas' disease.

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Citation Excerpt :
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