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, was previously hypothesised as a druggable target and vaccine candidate for human schistosomiasis. The purpose of this study is to characterize a purified recombinant G4LZI3 preliminarily for subsequent structural characterization, which will provide baseline structural data for future functional studies for the discovery, design and development of new schistosomal drugs for the treatment, control and elimination of schistosomiasis. Methods: Restriction digest analysis of a GenScript-synthesised codon-optimised G4LZI3 gene construct was carried out to ascertain its integrity and size. Thereafter, the pQE30-G4LZ13 construct was transformed into an M1.5 bacterial expression host. Transformed cells were induced with isopropyl beta-D-thiogalactoside for recombinant protein expression of an appreciable amount of pQE30-G4LZI3, which was subsequently purified with fast protein liquid chromatography (FPLC) and a size exclusion chromatographic purification scheme. Preliminary biophysical characterization of the 6X His-tagged G4LZI3 was done to determine its secondary structure characteristics and protein stability. Results: A molecular weight protein of 20.3 kDa was confirmed subsequent to restriction digest analysis, while heterologous protein expression yielded a highly soluble and considerable amount of histidine-tagged G4LZI3 protein, which was successfully purified to homogeneity. Biophysical characterization indicated that the protein was well folded, heat-stable, had the functional groups and secondary structure composition required and was thus amenable to further structural characterization and determination. Conclusion: Biophysical characterization of purified G4LZI3 showed that further structural studies can be embarked upon on the use of G4LZI3 as a druggable target and possibly a vaccine target against schistosomiasis via vaccinomics.