Binding of nitrogen‐containing bisphosphonates (N‐BPs) to the Trypanosoma cruzi farnesyl diphosphate synthase homodimer

Bisphosphonates (BPs) are a class of compounds that have been used extensively in the treatment of osteoporosis and malignancy‐related hypercalcemia. Some of these compounds act through inhibition of farnesyl diphosphate synthase (FPPS), a key enzyme in the synthesis of isoprenoids. Recently, nitrogen‐containing bisphosphonates (N‐BPs) used in bone resorption therapy have been shown to be active against Trypanosoma cruzi, the parasite that causes American trypanosomiasis (Chagas disease), suggesting that they may be used as anti‐trypanosomal agents. The crystal structures of TcFPPS in complex with substrate (isopentenyl diphosphate, IPP) and five N‐BP inhibitors show that the C‐1 hydroxyl and the nitrogen‐containing groups of the inhibitors alter the binding of IPP and the conformation of two TcFPPS residues, Tyr94 and Gln167. Isothermal titration calorimetry experiments suggest that binding of the first N‐BPs to the homodimeric TcFPPS changes the binding properties of the second site. This mechanism of binding of N‐BPs to TcFPPS is different to that reported for the binding of the same compounds to human FPPS. Proteins 2010. © 2009 Wiley‐Liss, Inc.