Plasmodium falciparum DDX31 is DNA helicase localized in nucleolus

Malaria is a major infectious disease and is responsible for millions of infections every year. As drug resistance strains of Plasmodium species are emerging, there is an urgent need to understand the parasite biology and identify new drug targets. Helicases are very important enzymes that participate in various nucleic acid metabolic processes. Previously we have reported several putative DEAD box helicases in the genome of Plasmodium falciparum 3D7 strain. In this study, we present biochemical characterization of one of the members of Has1 (Helicase associated with SET1) family of DEAD box proteins from P. falciparum 3D7 strain. PfDDX31 is a homologue of human DDX31 helicase and contains all the conserved characteristics motifs. The core PfDDX31C exhibits DNA and RNA dependent ATPase activity and unwinds partially duplex DNA by utilizing ATP or dATP only. The immunofluorescence assay results show that PfDDX31 is expressed throughout all the intraerythrocytic developmental stages in P. falciparum 3D7 strain. The co-localization with nucleolar marker PfNop1 further suggests that PfDDX31 is mostly present in nucleolus, a discrete nuclear compartment.