Functional and structural characterization of an ecotin-like serine protease inhibitor from Trypanosoma cruzi

Ecotin, a serine peptidase inhibitor (ISP), discovered in Escherichia coli, inhibit a wide range of trypsin-like serine peptidases, protecting microorganisms from the host's immune response. In eukaryotes, ISPs encoding genes were found only in Trypanosomatidae protozoa, including the genus Trypanosoma, which harbors Trypanosoma cruzi, the ethiological agent of Chagas' disease. T. cruzi encodes the ISP2 Trypanosomatidae orthologous, which in Leishmania species present inhibitory activity on mammalian proteases from S1A family suggesting its role in vertebrate-host-parasite interactions. In this study, the structural and biochemical characterization of the recombinant T. cruzi ISP2 (rTcISP2), produced in E. coli was purified in soluble form and analyzed by circular dichroism, fluorescence spectroscopy, native electrophoresis, dynamic light scattering, low X-ray scattering and homology modeling. The obtained data revealed that rTcISP2 was biologically active and forms homodimers in solution. Furthermore, inhibitory activity of rTcISP2 against human neutrophil elastase (HNE) is the highest among ISP2 orthologous from bacteria and trypanosomatids. The role of NE to control T. cruzi parasites through modulation of cellular and humoral innate immune responses in vertebrate hosts, make TcISP2 a key molecular component for parasite infection efficiency, providing a useful basis for investigation of host-parasite interactions and the potential of TcISP2 for biotechnological applications.