Targeting translation factor proteins holds promise for developing innovative anti-tuberculosis drugs. During protein translation, many factors cause ribosomes to stall at messenger RNA (mRNA). To maintain protein homeostasis, bacteria have evolved various ribosome rescue mechanisms, including the predominant trans-translation process, to release stalled ribosomes and remove aberrant mRNAs. The rescue systems require the participation of translation elongation factor proteins (EFs) and are essential for bacterial physiology and reproduction. However, they disappear during eukaryotic evolution, which makes the essential proteins and translation elongation factors promising antimicrobial drug targets. Here, we review the structural and molecular mechanisms of the translation elongation factors EF-Tu, EF-Ts, and EF-G, which play essential roles in the normal translation and ribosome rescue mechanisms of Mycobacterium tuberculosis (Mtb). We also briefly describe the structure-based, computer-assisted study of anti-tuberculosis drugs.

As the only translational factor that plays a critical role in two translational processes (elongation and ribosome regeneration), GTPase elongation factor G (EF-G) is a potential target for antimicrobial agents. Both Mycobacterium smegmatis and Mycobacterium tuberculosis have two EF-G homologous coding genes, MsmEFG1 (MSMEG_1400) and MsmEFG2 (MSMEG_6535), fusA1 (Rv0684) and fusA2 (Rv0120c), respectively. MsmEFG1 (MSMEG_1400) and fusA1 (Rv0684) were identified as essential genes for bacterial growth by gene mutation library and bioinformatic analysis. To investigate the biological function and characteristics of EF-G in mycobacterium, two induced EF-G knockdown strains (Msm-ΔEFG1(KD) and Msm-ΔEFG2(KD)) from Mycobacterium smegmatis were constructed by clustered regularly interspaced short palindromic repeats interference (CRISPRi) technique. EF-G2 knockdown had no effect on bacterial growth, while EF-G1 knockdown significantly retarded the growth of mycobacterium, weakened the film-forming ability, changed the colony morphology, and increased the length of mycobacterium. It was speculated that EF-G might be involved in the division of bacteria. Minimal inhibitory concentration assay showed that inhibition of EF-G1 expression enhanced the sensitivity of mycobacterium to rifampicin, isoniazid, erythromycin, fucidic acid, capreomycin and other antibacterial agents, suggesting that EF-G1 might be a potential target for screening anti-tuberculosis drugs in the future.

BACKGROUND: Elytrigia lolioides (Kar. et Kir.) Nevski, which is a perennial, cross-pollinating wheatgrass that is distributed in Russia and Kazakhstan, is classified into Elytrigia, Elymus, and Lophopyrum genera by taxonomists on the basis of different taxonomic classification systems. However, the genomic constitution of E. lolioides is still unknown. To identify the genome constitution and evolution of E. lolioides, we used single-copy nuclear genes acetyl-CoA carboxylase (Acc1) and elongation factor G (EF-G), multi-copy nuclear gene internal transcribed space (ITS), chloroplast gene trnL-F together with fluorescence and genomic in situ hybridization.
RESULTS: Despite the widespread homogenization of ITS sequences, two distinct lineages (genera Pseudoroegneria and Hordeum) were identified. Acc1 and EF-G sequences suggested that in addition to Pseudoroegneria and Hordeum, unknown genome was the third potential donor of E. lolioides. Data from chloroplast DNA showed that Pseudoroegneria is the maternal donor of E. lolioides. Data from specific FISH marker for St genome indicated that E. lolioides has two sets of St genomes. Both genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) results confirmed the presence of Hordeum genome in this species. When E genome was used as the probe, no signal was found in 42 chromosomes. The E-like copy of Acc1 sequences was detected in E. lolioides possibly due to the introgression from E genome species. One of the H chromosomes in the accession W6-26586 from Kazakhstan did not hybridize H genome signals but had St genome signals on the pericentromeric regions in the two-color GISH.
CONCLUSIONS: Phylogenetic and in situ hybridization indicated the presence of two sets of Pseudoroegneria and one set of Hordeum genome in E. lolioides. The genome formula of E. lolioides was designed as StStStStHH. E. lolioides may have originated through the hybridization between tetraploid Elymus (StH) and diploid Pseudoroegneria species. E and unknown genomes may participate in the speciation of E. lolioides through introgression. According to the genome classification system, E. lolioides should be transferred into Elymus L. and renamed as Elymus lolioidus (Kar. er Kir.) Meld.