Subcellular localization of PfPREX. Parasites were doubly transfected with pSSPF2/PfPREX-GFP and pSSPF2/PfACP-DsRED (A and B), or with pSSPF2/PfPREX-GFP alone (C and D). The mitochondrion of the pSSPF2/PfPREX-GFP single transfectant parasite (C and D) was stained with MitoTracker Red CM-H2XRos (MTR). Panels in each row represent: green signal of GFP (far left); red signal of DsRED specifically localizing to the apicoplast (A and B) or MTR to the mitochondrion (C and D) (second from the left); merge of the green and red signals as well as the blue signal of Hoechst 33342 indicating the position of the parasite nucleus (second from the right); overlay of the merged image with the phase contrast image (far right). (A) Early trophozoite; (B) Schizont; (C) Early trophozoite; (D) Schizont. Scale bar: 5 mm. PfREX localizes to the apicoplast. Seow F, Sato S, Janssen CS, Riehle MO, Mukhopadhyay A, Phillips RS, Wilson RJ, Barrett MP. The plastidic DNA replication enzyme complex of Plasmodium falciparum. Mol Biochem Parasitol. 2005 141:145-153. Copyright Elsevier 2009.

PfPrex primase traffics to the apicoplast and forms two foci during the intraerythrocytic cycle. The complete primase domain (AA1–465) of PfPrex was genetically fused to GFPmut2 and expressed from a nuclear plasmid in P. falciparum NF54 parasites. Indirect immunofluorescence microscopy with DAPI and antibodies against GFP and PfACP demonstrates clear apicoplast localization of PfPrex throughout the intraerythrocytic cycle. Differential interference contrast (DIC) images show typical appearances of both the parasite and the host RBC. Two foci appear within the apicoplast during the early trophozoite stage and then segregate to daughter merozoites during schizogony. Scale bar is 5 mm.Lindner SE, Llinás M, Keck JL, Kappe SH. The primase domain of PfPrex is a proteolytically matured, essential enzyme of the apicoplast. Mol Biochem Parasitol. 2011 180(2):69-75