Crystal Structures of TbCatB and Rhodesain, Potential Chemotherapeutic Targets and Major Cysteine Proteases of Trypanosoma brucei

Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America.
PLoS Neglected Tropical Diseases (Impact Factor: 4.45). 06/2010; 4(6):e701. DOI: 10.1371/journal.pntd.0000701
Source: PubMed


Trypanosoma brucei is the etiological agent of Human African Trypanosomiasis, an endemic parasitic disease of sub-Saharan Africa. TbCatB and rhodesain are the sole Clan CA papain-like cysteine proteases produced by the parasite during infection of the mammalian host and are implicated in the progression of disease. Of considerable interest is the exploration of these two enzymes as targets for cysteine protease inhibitors that are effective against T. brucei.
We have determined, by X-ray crystallography, the first reported structure of TbCatB in complex with the cathepsin B selective inhibitor CA074. In addition we report the structure of rhodesain in complex with the vinyl-sulfone K11002.
The mature domain of our TbCat*CA074 structure contains unique features for a cathepsin B-like enzyme including an elongated N-terminus extending 16 residues past the predicted maturation cleavage site. N-terminal Edman sequencing reveals an even longer extension than is observed amongst the ordered portions of the crystal structure. The TbCat*CA074 structure confirms that the occluding loop, which is an essential part of the substrate-binding site, creates a larger prime side pocket in the active site cleft than is found in mammalian cathepsin B-small molecule structures. Our data further highlight enhanced flexibility in the occluding loop main chain and structural deviations from mammalian cathepsin B enzymes that may affect activity and inhibitor design. Comparisons with the rhodesain*K11002 structure highlight key differences that may impact the design of cysteine protease inhibitors as anti-trypanosomal drugs.

Download full-text


Available from: Zachary B Mackey
  • Source
    • "Plakortide E showed selectivity towards the cathepsin-like cysteine proteases, with a non-competitive, reversible, and, in the case of rhodesain, a slow-binding inhibitory mode of action. The anti-protease activity of the compound may contribute to its anti-parasitic activity against Trypanosoma brucei, as rhodesain and also the cathepsin B like protease TbCatB [13] are known to be essential for the parasite’s growth and pathogenicity. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we report new protease inhibitory activity of plakortide E towards cathepsins and cathepsin-like parasitic proteases. We further report on its anti-parasitic activity against Trypanosoma brucei with an IC50 value of 5 μM and without cytotoxic effects against J774.1 macrophages at 100 μM concentration. Plakortide E was isolated from the sponge Plakortis halichondroides using enzyme assay-guided fractionation and identified by NMR spectroscopy and mass spectrometry. Furthermore, enzyme kinetic studies confirmed plakortide E as a non-competitive, slowly-binding, reversible inhibitor of rhodesain.
    Full-text · Article · May 2014 · Marine Drugs
  • Source
    • "The CPs are also of interest because of their structural differences with the mammalian CPs. The protein tbcatB has been crystallized and its structure confirms an occluding loop which is important for substrate binding (Kerr et al. 2010). This loop creates a larger prime side pocket in active site cleft than is found in mammalian cathepsin B. The difference in the structure of the proteins may be utilized for design of inhibitors. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Leishmaniasis is a major public health problem and till date there are no effective vaccines available. The control strategy relies solely on chemotherapy of the infected people. However, the present repertoire of drugs is limited and increasing resistance towards them has posed a major concern. The first step in drug discovery is to identify a suitable drug target. The genome sequences of Leishmania major and Leishmania infantum has revealed immense amount of information and has given the opportunity to identify novel drug targets that are unique to these parasites. Utilization of this information in order to come up with a candidate drug molecule requires combining all the technology and using a multi-disciplinary approach, right from characterizing the target protein to high throughput screening of compounds. Leishmania belonging to the order kinetoplastidae emerges from the ancient eukaryotic lineages. They are quite diverse from their mammalian hosts and there are several cellular processes that we are getting to know of, which exist distinctly in these parasites. In this review, we discuss some of the metabolic pathways that are essential and could be used as potential drug targets in Leishmania.
    Full-text · Article · Apr 2010 · Journal of parasitic diseases
  • [Show abstract] [Hide abstract]
    ABSTRACT: Treating tropical diseases: Structure‐based design afforded highly active triazine nitrile inhibitors of the protozoan cysteine proteases falcipain‐2 and rhodesain. Optimization of the occupancy of the S1, S2, and S3 pockets of these enzymes yielded inhibitory constants in the low nanomolar activity range. The new ligands are selective against other related proteases and exhibit in vitro activities against the protozoan parasites.
    No preview · Article · Feb 2011 · ChemMedChem
Show more