Lilach Sheiner, Jana Ovciarikova, Andrew E Maclean, Alice Lacombe, Paula Fernandes, Alexander Mühleip, Julie Tottey, University of Glasgow, Infectiologie et Santé Publique (UMR ISP), Institut National de la Recherche Agronomique (INRA)-Université de Tours, Stockholm University, BBSRC (BB/N003675/1), and Institut National de la Recherche Agronomique (INRA)-Université de Tours (UT)
Summary Apicomplexan parasites cause diseases such as malaria and toxoplasmosis. The apicomplexan mitochondrion shows striking differences from common model organisms, including fundamental processes such as mitochondrial translation. Despite evidence that mitochondrial translation is essential for parasite survival, it is largely understudied. Progress has been restricted by the absence of functional assays to detect apicomplexan mitochondrial translation, a lack of knowledge of proteins involved in the process and the inability to identify and detect mitoribosomes. We report the localization of 12 new mitochondrial proteins, including 6 putative mitoribosomal proteins. We demonstrate the integration of three mitoribosomal proteins in macromolecular complexes, and provide evidence suggesting these are apicomplexan mitoribosomal subunits, detected here for the first time. Finally, a new analytical pipeline detected defects in mitochondrial translation upon depletion of the small subunit protein 35 (TgmS35), while other mitochondrial functions remain unaffected. Our work lays a foundation for the study of apicomplexan mitochondrial translation., The apicomplexan mitochondrion is divergent and essential yet poorly studied. Mitochondrial translation is predicted to utilise ribosomes assembled from fragmented rRNA but this was never shown. Lack of tools to study mitochondrial translation in apicomplexan has been a long‐standing challenge. Tagging and depletion of T. gondii mitoribosomal proteins enabled the first detection of a ribosomal complex, and provided proof of principle for a new mitochondrial translation analytic pipeline.