Plasmodium falciparum RuvB2 translocates in 5'-3' direction, relocalizes during schizont stage and its enzymatic activities are up regulated by RuvB3 of the same complex.

Two similar proteins RuvB like1 (Rvb1/Pontin) and RuvB like2 (Rvb2/Reptin) of AAA+ family of enzymes are present in yeast to human and are well known to be involved in diverse cellular activities. The human malaria parasite Plasmodium falciparum contains three different RuvB like proteins. Thus it has been of interest to explore why P. falciparum requires three RuvB like proteins and how these enzymes are biochemically regulated. In this study, we present the detailed biochemical characterization of PfRuvB2. The complex of PfRuvB3 was immunopurified and the presence of PfRuvB2 was confirmed. The in vitro interaction study shows that PfRuvB2 interacts only with PfRuvB3 but not with PfRuvB1. The recombinant as well as endogenous PfRuvB2 contains ATPase as well as weak DNA helicase activities. The presence of PfRuvB3 in the helicase reaction of PfRuvB2 increases the helicase activity significantly. Interestingly PfRuvB2/PfRuvB3 complex preferentially translocates and unwinds DNA in the 5'-3' direction. In vivo studies showed that PfRuvB2 is expressed in all the asexual intraerythrocytic developmental stages and localizes mainly in the nucleus during merozoite, ring and trophozoite stages while during schizont stage it relocalizes partially in the nucleus and partially towards cytoplasm. As PfRuvB3 is specific to intraerythrocytic mitosis so we interpret that PfPuvB3 interacts with PfRuvB2 during schizont/intraerythrocytic mitosis and acts as its modulator mainly for the appreciable helicase activity.