Plasmodium falciparum: functional mitochondrial ADP/ATP transporter in Escherichia coli plasmic membrane as a tool for selective drug screening

Plasmodium falciparum mitochondrial ADP/ATP transporter or adenylate translocase (PfAdT) was previously characterised at the molecular level and intracellularly located by immuno-electromicroscopy. Inhibition of this transporter blocks parasite development in erythrocytes. In this study, PfAdT was expressed in C43 (DE3) Escherichia coli strain under isopropyl beta-d-thiogalacto-pyranoside (IPTG) induction to screen inhibitory molecules. PfAdT was integrated directly into the bacterial cytoplasmic membrane. Whereas IPTG-induced bacterial cells imported radioactively labelled ATP, non-induced cells did not. The transporter bound specifically ADP and ATP, but not AMP. IPTG-induced cells preloaded with labelled ATP exported ATP after exogenous addition of unlabelled ADP or ATP, indicating a counter exchange transport mechanism. Bongrekic acid and atractyloside, two well-known specific inhibitors of mitochondrial ADP/ATP transporter, were tested. This experimental model was evaluated using three Malagasy crude plants extracts which have shown antiplasmodial activity on in vitro parasite cultures.