Purification and characterization of a novel 3'-5' DNA helicase from Plasmodium falciparum and its sensitivity to anthracycline antibiotics.

Plasmodium falciparum has developed resistance to most anti-malarials; therefore, an investigation of potential targets should be performed. DNA helicases are enzymes that catalyse the unwinding of double-stranded DNA to provide single-stranded templates for DNA replication, repair and recombination. In this study, a DNA helicase (PfDH A) was purified from a crude extract of Plasmodium falciparum. DNA helicase activity was measured by assaying unwinding activity. The apparent molecular weight of PfDH A as determined by SDS-PAGE was 90 kDa. PfDH A moved unidirectionally in the 3' -to- 5' direction along the bound strand and preferred a fork-like substrate structure and could not unwind blunt-ended duplex DNA. Unwinding activity required Mg2+ and could be inhibited by 200 mM NaCl or KCl and was dependent on hydrolysis of ATP or dATP. Anthracyclines, including daunorubicin, nogalamycin, doxorubicin, and aclarubicin, inhibited PfDH A activity with IC50 values of 2, 5, 8 and 9 microM, respectively. Based on the results, PfDH A differs from all known human DNA helicases. However, its function and roles in parasite DNA replication need to be elucidated in the future.