Fragmented rRNAs and lineage-specific RNA-binding proteins define myzozoan mitoribosomes.

Myzozoa, a clade of alveolate protists including Apicomplexa, Chromerida, Perkinsozoa, and dinoflagellates, possesses the most reduced mitochondrial genomes among eukaryotes. Apicomplexan parasites, such as Toxoplasma gondii and Plasmodium spp., retain mitochondrial genomes encoding only three proteins and highly fragmented rRNAs. Despite this reduction, recent structural studies show that T. gondii mitoribosome incorporates lineage-specific RNA-binding proteins as integral components to maintain a functional complex composed of over 50 rRNA fragments. The conservation of rRNA fragmentation and protein repertoire observed among Apicomplexa suggests a shared evolution within the phylum. This radical divergence from all other currently investigated cytoplasmic and mitochondrial ribosomes highlights evolutionary plasticity and common ancestry, providing a model for studying mitochondrial evolution and potential antiparasitic drug discovery.