Abstract
For the past five decades, Praziquantel (PZQ) has been the only drug used for the treatment of
schistosomiasis. However, despite its long-standing efficiency, its mechanism of action still
remains unelucidated. In addition, recent studies have reported the emergence of PZQ-resistant
schistosomes. This raises the need to understand the molecular interactions in schistosome
biology, which is critical for predicting resistance patterns and developing alternative
therapeutic methods. This study explored the interaction between the S. mansoni Universal
stress G4LZI3 protein and selected divalent cations potentially involved in the PZQ molecular
mechanism. Given its proposed role in parasite survival under stress conditions, the G4LZI3
protein was further explored as a potential target for drug development against schistosomiasis.
Sufficient amounts of the G4LZI3 protein were recombinantly expressed using 0.5 mM IPTG
and purified to homogeneity on a His-Select Cobalt resin. The pure protein was then dialyzed
and concentrated down for interaction studies with Mg2+, Ca2+, and Zn2+. Additionally,
computational studies were conducted to find potential inhibitors of the G4LZI3 protein. UVvis
and Raman's spectroscopy showed substantial binding of divalent cations to the protein.
The Microscale Thermophoresis studies revealed moderate binding affinities between the
divalent cations and the protein, with Mg2+ being the most significant binding (KD= 0.004 μM),
suggesting these divalent cations function as structural cofactors. MD simulations revealed
three compounds that achieved significant stability and favorable interactions with G4LZI3
protein with superior RMSD stability (~3.17 Å) compared to PZQ (~4.70 Å), suggesting better
structural retention. These findings lay the groundwork for uncovering the molecular
mechanisms of PZQ and exploring the potential of S. mansoni G4LZI3 analogs as therapeutic
agents against schistosomiasis.