Reduced ribosomes of the apicoplast and mitochondrion of Plasmodium spp. and predicted interactions with antibiotics

Abstract

Apicomplexan protists such as Plasmodium and Toxoplasma contain a mitochondrion and a relic plastid (apicoplast) that are sites of protein translation. Although there is emerging interest in the partitioning and function of translation factors that participate in apicoplast and mitochondrial peptide synthesis, the composition of organellar ribosomes remains to be elucidated. We carried out an analysis of the complement of core ribosomal protein subunits that are encoded by either the parasite organellar or nuclear genomes, accompanied by a survey of ribosome assembly factors for the apicoplast and mitochondrion. A cross-species comparison with other apicomplexan, algal and diatom species revealed compositional differences in apicomplexan organelle ribosomes and identified considerable reduction and divergence with ribosomes of bacteria or characterized organelle ribosomes from other organisms. We assembled structural models of sections of Plasmodium falciparum organellar ribosomes and predicted interactions with translation inhibitory antibiotics. Differences in predicted drug–ribosome interactions with some of the modelled structures suggested specificity of inhibition between the apicoplast and mitochondrion. Our results indicate that Plasmodium and Toxoplasma organellar ribosomes have a unique composition, resulting from the loss of several large and small subunit proteins accompanied by significant sequence and size divergences in parasite orthologues of ribosomal proteins.

Identification of the Toxoplasma gondii mitochondrial ribosome, and characterisation of a protein essential for mitochondrial translation

“…This search identified 43 genes (Table – sheet 2 – column A). In support of some enrichment of translation components in this dataset, we found 5 of the 35 predicted mitochondrial ribosomal proteins (Gupta et al , ) in the 43‐gene dataset, while none of them is found in five lists of 43 randomly chosen genes (Table – sheet 2 – columns C‐O). We attempted to localise the protein product of 14 genes from this focused dataset.…”

“…Among the above 10 genes we localised to the T. gondii mitochondrion, 4 are predicted to encode mitoribosomal proteins (Table and Fig. A): TGME49_201830/226280/312680 are predicted to encode the mitochondrial large subunit components 54, 28 and 41, respectively, thus we named them Tg mL54, Tg bL28m and Tg mL41; TGME49_203620, while annotated as hypothetical protein in http://ToxoDB.org, is a putative homolog of the mitochondrial small subunit 35 (mS35) (Gupta et al , ; Greber and Ban, ), we, therefore, named it, Tg m S35 . To provide support for this prediction, we tested the gel migration patterns of endogenously triple‐HA tagged Tg m S35 .…”

“… Putative mitoribosomal proteins were identified through our mRNA expression based screen (Fig. ) and/or identified bioinformatically in Gupta et al () ‘Reduced ribosomes of the apicoplast and mitochondrion of Plasmodium spp. and predicted interactions with antibiotics’.…”

Chloramphenicol acetyltransferase—a new selectable marker in stable nuclear transformation of the red alga Cyanidioschyzon merolae

“…Yet, it must also be stated that the sensitivity of both: mitochondrial and chloroplast ribosomes to chloramphenicol have also been demonstrated in other organisms (Ellis 1968;SmithJohannsen and Gibbs 1972;Margulies and Brubaker 1970;Chrzanowska-Lightowlers et al 1994;Yunis et al 1973;Houtkooper et al 2013;Kearsey and Craig 1981;Stegeman and Hoober 1974). The level of sensitivity of plastid ribosomes to chloramphenicol seems to be a species-specific issue, what have been recently demonstrated by Gupta et al (2014). The protein content and structure of mitochondrial ribosomal machinery of a few species have been compared, among them C. merolae, revealing several species-specific differences.…”

Polypeptide release factors and stop codon recognition in the apicoplast and mitochondrion of Plasmodium falciparum

“…Translation of genes encoded by the apicoplast and mitochondrion of P. falciparum is mediated by translation factors encoded by the nuclear genome, with the exception of apicoplast‐encoded EF‐Tu. These factors interact with the reduced and divergent ribosomes (Gupta et al ., ) of the parasite organelles. Initiation factors IF1 and IF3, elongation factors EF‐Tu, EF‐Ts and EF‐G and ribosome recycling factor RRF1 functioning in the apicoplast have been characterized recently and IF2, IF3, EF‐Tu, EF‐G and RRF2 have been identified for parasite mitochondrial translation (Biswas et al ., ; Jackson et al ., ; Johnson et al ., ; Gupta et al ., ; Haider et al ., ).…”