Conventional tRNAs have highly conserved sequences, four-armed cloverleaf secondary structures, and L-shaped tertiary structures. However, metazoan mitochondrial tRNAs contain several exceptional structures. Almost all tRNASers for AGY/N codons lack the D-arm. Furthermore, in some nematodes, no four-armed cloverleaf-type tRNAs are present: two tRNAsSer without the D-arm and 20 tRNAs without the T-arm are found. Previously, we showed that in nematode mitochondria, an extra elongation factor Tu (EF-Tu) has evolved to support interaction with tRNAs lacking the T-arm, which interact with C-terminal domain 3 in conventional EF-Tu. Recent mitochondrial genome analyses have suggested that in metazoan lineages other than nematodes, tRNAs without the T-arm are present. Furthermore, even more simplified tRNAs are predicted in some lineages. In this review, we discuss mitochondrial tRNAs with divergent structures, as well as protein factors, including EF-Tu, that support the function of truncated metazoan mitochondrial tRNAs.

Malaria is one of the three major global health threats. Drug development for malaria, especially for its most dangerous form caused by Plasmodium falciparum, remains an urgent task due to the emerging drug-resistant parasites. Exploration of novel antimalarial drug targets identified a trifunctional enzyme, malate quinone oxidoreductase (MQO), located in the mitochondrial inner membrane of P. falciparum (PfMQO). PfMQO is involved in the pathways of mitochondrial electron transport chain, tricarboxylic acid cycle, and fumarate cycle. Recent studies have shown that MQO is essential for P. falciparum survival in asexual stage and for the development of experiment cerebral malaria in the murine parasite P. berghei, providing genetic validation of MQO as a drug target. However, chemical validation of MQO, as a target, remains unexplored. In this study, we used active recombinant protein rPfMQO overexpressed in bacterial membrane fractions to screen a total of 400 compounds from the Pathogen Box, released by Medicines for Malaria Venture. The screening identified seven hit compounds targeting rPfMQO with an IC₅₀ of under 5 μM. We tested the activity of hit compounds against the growth of 3D7 wildtype strain of P. falciparum, among which four compounds showed an IC₅₀ from low to sub-micromolar concentrations, suggesting that PfMQO is indeed a potential antimalarial drug target.

Background: Mitochondrial (mt) genomes vary considerably in size, structure and gene content. The mt genomes of the phylum Apicomplexa, which includes important human pathogens such as the malaria parasite Plasmodium, also show marked diversity of structure. Plasmodium has a concatenated linear mt genome of the smallest size (6-kb); Babesia and Theileria have a linear monomeric mt genome (6.5-kb to 8.2-kb) with terminal inverted repeats; Eimeria, which is distantly related to Plasmodium and Babesia/Theileria, possesses a mt genome (6.2-kb) with a concatemeric form similar to that of Plasmodium; Cryptosporidium, the earliest branching lineage within the phylum Apicomplexa, has no mt genome. We are interested in the evolutionary origin of linear mt genomes of Babesia/Theileria, and have investigated mt genome structures in members of archaeopiroplasmid, a lineage branched off earlier from Babesia/Theileria. Results: The complete mt genomes of archaeopiroplasmid parasites, Babesia microti and Babesia rodhaini, were sequenced. The mt genomes of B. microti (11.1-kb) and B. rodhaini (6.9-kb) possess two pairs of unique inverted repeats, IR-A and IR-B. Flip-flop inversions between two IR-As and between two IR-Bs appear to generate four distinct genome structures that are present at an equi-molar ratio. An individual parasite contained multiple mt genome structures, with 20 copies and 2 – 3 copies per haploid nuclear genome in B. microti and B. rodhaini, respectively. Conclusion: We found a novel linear monomeric mt genome structure of B. microti and B. rhodhaini equipped with dual flip-flop inversion system, by which four distinct genome structures are readily generated. To our knowledge, this study is the first to report the presence of two pairs of distinct IR sequences within a monomeric linear mt genome. The present finding provides insight into further understanding of evolution of mt genome structure.

Background: We previously found the first examples of splicing of archaeal pre-mRNAs for homologs of the eukaryotic CBF5 protein (also known as dyskerin in humans) inAeropyrum pernix, Sulfolobus solfataricus, S. tokodaii, andS. acidocaldarirus, and also showed that crenarchaeal species in orders Desulfurococcales and Sulfolobales, except forHyperthermus butylicus, Pyrodictium occultum, Pyrolobus fumarii, andIgnicoccus islandicus, contain the (putative)cbf5intron. However, the exact timing of the intron insertion was not determined and verification of the putative secondary loss of the intron in some lineages was not performed.Results: In the present study, we determined approximately two-thirds of the entire coding region of crenarchaeal Cbf5 sequences from 43 species. A phylogenetic analysis of our data and information from the available genome sequences suggested that the (putative)cbf5intron existed in the common ancestor of the orders Desulfurococcales and Sulfolobales and that probably at least two independent lineages in the order Desulfurococcales lost the (putative) intron.Conclusion: This finding is the first observation of a lineage-specific loss of a pre-mRNA intron in Archaea. As the insertion or deletion of introns in protein-coding genes in Archaea has not yet been seriously considered, our finding suggests the possible difficulty of accurately and completely predicting protein-coding genes in Archaea.

Background: Urogenital schistosomiasis (UgS) is a parasitic disease caused by Schistosoma haematobium and can lead to chronic ill-health. Nigeria is endemic for schistosomiasis, but epidemiology of UgS has not been studied in most states. This study was conceived with the aim to contribute towards an accurate national picture of UgS in Nigeria. The prevalence of UgS and the associated risk factors were for the first time investigated among primary school pupils in Jidawa and Zobiya communities of the Dutse Local Government Area (LGAs) of Jigawa State, Nigeria.Method: Focus group discussions with teachers and parents were conducted. After obtaining written consent from parents, questionnaires were administered to pupils to obtain socio-demographic data and information on water contact activities. Urine samples (279) were collected and processed by the urine filtration technique to evaluate haematuria and the presence of S. haematobium eggs.Results: Prevalences of 65.7% (90/137) and 69.0% (98/142) were recorded in the Jidawa and Zobiya communities, respectively. In both communities, there was a significant association between gender and UgS: 63.3% of the infected pupils were males as compared to 36.7% females (χ2 = 5.42, p = 0.020). Grade 5 students had a significantly higher prevalence (χ2 = 17.919, p = 0.001) (80.0%) compared to those in grades 2, 3, 4, and 6 (63.8%, 66.7%, 61.5%, and 64.6%, respectively). Water contact activities showed that pupils involved in fishing, irrigation, and swimming were at greater risk of becoming infected in Jidawa and Zobiya, with odds ratios (risk factors) of 5.4 (0.994–28.862) and 4.1 (1.709–9.862), respectively (p = 0.05).Conclusion: Both the Jidawa and Zobiya communities of the Dutse LGAs of Jigawa State are hyperendemic for UgS. In collaboration with the State Ministry of Health, mass administration of praziquantel was carried out in the Jidawa and Zobiya communities after this study.