Molecular cloning, characterization and expression profile of a glutathione peroxidase-like thioredoxin peroxidase (TPxGl) of the rodent malaria parasite Plasmodium berghei

Abstract

Glutathione peroxidases (GPx) comprise an important group of redox active proteins with diverse functions, including antioxidant defense and signaling. Although the genome of the malaria parasite Plasmodium does not contain a genuine GPx gene a glutathione peroxidase-like thioredoxin peroxidase (TPx(Gl)) has recently been identified and biochemically characterized in the human malaria parasite P. falciparum. To gain more insight into the potential biological function of this enzyme we have cloned and expressed TPx(Gl) of the rodent model system P. berghei (PbTPx(Gl)). Biochemical characterization confirmed that the protein is redox active with the P. berghei thioredoxin system. We compared PbTPx(Gl) to recently characterized thioredoxin-dependent GPx-type proteins of other organisms, and generated the first hypothetical 3D model of a Plasmodium TPx(Gl), which shows the conservation of the thioredoxin-fold as well as the spatial orientation of a classic GPx catalytic tetrad. In vivo studies indicate that PbTPx(Gl) is continuously expressed in all P. berghei asexual blood stages, gametocytes and in early mosquito-stage parasites. Confocal microscopy suggest a cytoplasmic localization of PbTPx(Gl) in all investigated parasite life stages, specifically in mature ookinetes. Our data provides new insights into the structure and ubiquitous expression of Plasmodium TPx(Gl) and warrants further investigation into this potentially important redox enzyme.

Keywords: Cellular expression; Enzymatic activity; Glutathione peroxidase-like; Malaria; Ookinete; Plasmodium berghei; Protein modeling.