Plasmodium, the Apicomplexa Outlier When It Comes to Protein Synthesis

Plasmodium is an obligate intracellular parasite that has numerous interactions with different hosts during its elaborate life cycle. This is also the case for the other parasites belonging to the same phylum Apicomplexa. In this study, we bioinformatically identified the components of the multi-synthetase complexes (MSCs) of several Apicomplexa parasites and modelled their assembly using AlphaFold2. It appears that none of these MSCs resemble the two MSCs that we have identified and characterized in Plasmodium. Indeed, tRip, the central protein involved in the association of the two Plasmodium MSCs is different from its homologues, suggesting also that the tRip-dependent import of exogenous tRNAs is not conserved in other apicomplexan parasites. Based on this observation, we searched for obvious differences that could explain the singularity of Plasmodium protein synthesis by comparing tRNA genes and amino acid usage in the different genomes. We noted a contradiction between the large number of asparagine residues used in Plasmodium proteomes and the single gene encoding the tRNA that inserts them into proteins. This observation remains true for all the Plasmodia strains studied, even those that do not contain long asparagine homorepeats.