Evidence of Ternary Complex Formation in Trypanosoma cruzi trans-Sialidase Catalysis

Trypanosoma cruzi trans-sialidase (TcTS) is a key target protein for Chagas disease chemotherapy. In this study, we investigated the implications of active site flexibility on the biochemical mechanism of TcTS. Molecular dynamics studies revealed remarkable plasticity in the TcTS catalytic site, demonstrating, for the first time, how donor substrate engagement with the enzyme induces an acceptor binding site in the catalytic pocket that was not previously captured in crystal structures. Furthermore, NMR data showed cooperative binding between donor and acceptor substrates, supporting theoretical results. In summary, our data put forward a coherent dynamic framework to understand how a glycosidase evolved its highly efficient trans-glycosidase activity. Trypanosoma cruzi trans-sialidase (TcTS) is a potential target for Chagas disease chemotherapy. The binding of a sialoside donor opens a second cavity that supports acceptor substrate binding. The cooperative binding of both substrates to TcTS is required for transfer reaction. This is the first time that the acceptor substrate binding site is shown in TcTS.