Ribosomal architecture and rRNA modification landscape in the tick-borne parasite Babesia divergens.

Babesia are tick-borne intracellular apicomplexan parasites that infect a wide range of wild and domestic animals (e.g., cattle), resulting in significant economic losses to the livestock industry. Humans are considered accidental hosts for a few Babesia species. Babesia microti and B. divergens are the most prevalent causes of human babesiosis that are showing a broadening geographic distribution. Due to the complex life cycle of Babesia species, their survival depends on the precise control of gene expression, which is primarily regulated by epigenetic, transcriptional, and post-transcriptional mechanisms. High-resolution structural information on key components of the translation machinery, such as ribosomes, could aid in the development of antiparasitic drugs. Here, we report cryogenic electron microscopy ribosome structures from B. divergens, showing associated tRNAs, an mRNA fragment, and RACK1, a signaling scaffold crucial to translation regulation. Density map analysis displays ribosome regions at high resolution, which, when combined with nanopore sequencing, enabled the comprehensive identification of rRNA modifications. The rRNA modifications localize not only to the reduced B. divergens rRNA expansion segments but also to functionally essential ribosomal sites.