Glutathione Reductase of Plasmodium Falciparum as an Antimalarial Drug Target of Methylene Blue

Abstract

Plasmodium falciparum is the cause of human malaria and is one of two malaria parasites known to have drug resistance. Since there are no preventative vaccinations against malaria, the control of this disease is heavily dependent upon the use of antimalarial drugs. Antimalarial drugs, such as methylene blue, are effective therapies against human malaria. At a specific concentration, methylene blue has been shown to be a selective inhibitor of the parasite's glutathione reductase (PfGR). Glutathione reductase is an important target when studying malaria drug resistance because it is a flavoenzyme that regenerates glutathione, which is an essential protein for antioxidant defense against cell damage. Methylene blue is also a substrate that is reduced by gluthathione reductase to produce leucoMB. This is then spontaneously oxidized by molecular oxygen to form methylene blue again. During this process, reactive oxygen species, such as hydrogen peroxide and superoxide form. These act as recycling catalysts against infectious organisms. Due to PfGR's central position in redox control, it is ranked number one as an antimalarial drug target. The goal of this research is to study the interface between methylene blue and the putative protein target, glutathione reductase, in order to understand the drug action mechanism. PfGR was expressed and purified and hydrogen-deuterium exchange (HDX) will be used to map the drug-protein interface. We will present the mass spectrometry data for the solvent exposed peptides after digestion with pepsin when PfGR is complexed with methylene blue, which will allow us to narrow down the active site.