research papers
American trypanosomiasis, commonly known as Chagas disease, is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. The chronic form of the infection often causes debilitating morbidity and mortality. However, the current treatment for the disease is typically inadequate owing to drug toxicity and poor efficacy, necessitating a continual effort to discover and develop new antiparasitic therapeutic agents. The structure of T. cruzi histidyl-tRNA synthetase (HisRS), a validated drug target, has previously been reported. Based on this structure and those of human cytosolic HisRS, opportunities for the development of specific inhibitors were identified. Here, efforts are reported to identify small molecules that bind to T. cruzi HisRS through fragment-based crystallographic screening in order to arrive at chemical starting points for the development of specific inhibitors. T. cruzi HisRS was soaked into 68 different cocktails from the Medical Structural Genomics of Pathogenic Protozoa (MSGPP) fragment library and diffraction data were collected to identify bound fragments after soaking. A total of 15 fragments were identified, all bound to the same site on the protein, revealing a fragment-binding hotspot adjacent to the ATP-binding pocket. On the basis of the initial hits, the design of reactive fragments targeting the hotspot which would be simultaneously covalently linked to a cysteine residue present only in trypanosomatid HisRS was initiated. Inhibition of T. cruzi HisRS was observed with the resultant reactive fragments and the anticipated binding mode was confirmed crystallographically. These results form a platform for the development of future generations of selective inhibitors for trypanosomatid HisRS.
Keywords: fragment-based crystallographic cocktail screening; structure-guided drug discovery; inhibitor of histidyl-tRNA synthetase; trypanosomiasis; reactive fragment.
Supporting information
Portable Document Format (PDF) file https://doi.org/10.1107/S1399004715007683/dz5371sup1.pdf |
PDB references: Trypanosoma cruzi HisRS, complex with Chem 79, 4yp0; complex with Chem 84, 4ypf; complex with Chem 89, 4yrc; complex with Chem 145, 4yre; complex with Chem 148, 4yrf; complex with Chem 149, 4yrg; complex with Chem 166, 4yri; complex with Chem 256, 4yrj; complex with Chem 262, 4yrl; complex with Chem 260, 4yrk; complex with Chem 443, 4yrm; complex with Chem 475, 4yrn; complex with Chem 491, 4yro; complex with Chem 707, 4yrp; complex with Chem 744, 4yrq; complex with Chem 1691, 4yrr; complex with Chem 1698, 4yrs; complex with Chem 1781, 4yrt