Localization of the putative recombinase Pf-int to the apicoplast of Plasmodium falciparum

Diseases caused by apicomplexan parasites, such as malaria and toxoplasmosis cause ∼200 million (worldwide) and 1 million (Europe) infections, respectively, every year. Apicomplexa possess a non-photosynthetic organelle homologous to the plant chloroplast, the so-called apicoplast, that is essential for their growth and survival. This study focused on the Int recombinase, the first protein discovered in Plasmodium spp . with the features of a site-specific recombinase, and which has an apicoplast targeting leader sequence at its amino-terminus. Int is conserved amongst several apicomplexan parasites. In the human toxoplasmosis parasite, Toxoplasma , Int localizes to the apicoplast and Pf-Int, the P. falciparum member, belongs to the group of non-mutable essential genes in P. falciparum . A conserved protein that has been shown to be essential at least in one species and that localizes to an essential organelle may become a novel drug target. Therefore, the aim of this study was to confirm the sub-cellular localization of Int in the human malaria parasite P. falciparum . Using western blot analysis and immunofluorescence microscopy of P. falciparum asexual blood stages, we observed that Int partially co-localized with the apicoplast (to discrete foci adjacent to the nucleus). ### Competing Interest Statement I have read BioRxiv policy and the authors of this manuscript have the following competing interests: AVB declares a potential conflict of interest in terms of funding for the PhD thesis by Merck KGaA (Direct: employment, stock ownership, grants, patents). This does not alter our adherence to BioRxiv policies on sharing data and materials. On behalf of all other authors, the corresponding author declares that there are no conflicts of interest.