Recombinant Expression and Biophysical Characterization of a Druggable Schistosoma mansoni Universal Stress G4LZI3 Protein.

Purpose: Universal stress protein (USP) from Schistosoma mansoni, designated as G4LZI3, waspreviously hypothesised as a druggable target and vaccine candidate for human schistosomiasis.The purpose of this study is to characterize a purified recombinant G4LZI3 preliminarily forsubsequent structural characterization, which will provide baseline structural data for futurefunctional studies for the discovery, design and development of new schistosomal drugs for thetreatment, control and elimination of schistosomiasis. Methods: Restriction digest analysis of a GenScript-synthesised codon-optimised G4LZI3gene construct was carried out to ascertain its integrity and size. Thereafter, the pQE30-G4LZI3 construct was transformed into an M15 bacterial expression host. Transformed cellswere induced with isopropyl ß-D-thiogalactoside for recombinant protein expression of anappreciable amount of pQE30-G4LZI3, which was subsequently purified with fast proteinliquid chromatography (FPLC) and a size exclusion chromatographic purification scheme.Preliminary biophysical characterization of the 6X His-tagged G4LZI3 was done to determineits secondary structure characteristics and protein stability. Results: A molecular weight protein of 20.3 kDa was confirmed subsequent to restriction digestanalysis, while heterologous protein expression yielded a highly soluble and considerableamount of histidine-tagged G4LZI3 protein, which was successfully purified to homogeneity.Biophysical characterization indicated that the protein was well folded, heat-stable, had thefunctional groups and secondary structure composition required and was thus amenable tofurther structural characterization and determination. Conclusion: Biophysical characterization of purified G4LZI3 showed that further structuralstudies can be embarked upon on the use of G4LZI3 as a druggable target and possibly avaccine target against schistosomiasis via vaccinomics.

Proteins as Targets in Anti-Schistosomal Drug Discovery and Vaccine Development.

Proteins hardly function in isolation; they form complexes with other proteins or molecules to mediate cell signaling and control cellular processes in various organisms. Protein interactions control mechanisms that lead to normal and/or disease states. The use of competitive small molecule inhibitors to disrupt disease-relevant protein-protein interactions (PPIs) holds great promise for the development of new drugs. Schistosome invasion of the human host involves a variety of cross-species protein interactions. The pathogen expresses specific proteins that not only facilitate the breach of physical and biochemical barriers present in skin, but also evade the immune system and digestion of human hemoglobin, allowing for survival in the host for years. However, only a small number of specific protein interactions between the host and parasite have been functionally characterized; thus, in-depth understanding of the molecular mechanisms of these interactions is a key component in the development of new treatment methods. Efforts are now focused on developing a schistosomiasis vaccine, as a proposed better strategy used either alone or in combination with Praziquantel to control and eliminate this disease. This review will highlight protein interactions in schistosomes that can be targeted by specific PPI inhibitors for the design of an alternative treatment to Praziquantel.