Mitochondrial genome has undergone significant reduction in a course of evolution; however, it still contains a set of protein-encoding genes and requires translational machinery for their expression. Mitochondrial translation is of the prokaryotic type with several remarkable differences. This review is dedicated to one of the most puzzling features of mitochondrial protein synthesis, namely, the system of translational activators, i.e., proteins that specifically regulate translation of individual mitochondrial mRNAs and couple protein biosynthesis with the assembly of mitochondrial respiratory chain complexes. The review does not claim to be a comprehensive analysis of all published data; it is rather focused on the idea of the "core component" of the translational activator system.

BackgroundThe GTPase eEF1A is the eukaryotic factor responsible for the essential, universal function of aminoacyl-tRNA delivery to the ribosome. Surprisingly, eEF1A is not universally present in eukaryotes, being replaced by the paralog EFL independently in multiple lineages. The driving force behind this unusually frequent replacement is poorly understood.ResultsThrough sequence searching of genomic and EST databases, we find a striking association of eEF1A replacement by EFL and loss of eEF1A’s guanine exchange factor, eEF1Bα, suggesting that EFL is able to spontaneously recharge with GTP. Sequence conservation and homology modeling analyses indicate several sequence regions that may be responsible for EFL’s lack of requirement for eEF1Bα.ConclusionsWe propose that the unusual pattern of eEF1A, eEF1Bα and EFL presence and absence can be explained by a ratchet-like process: if either eEF1A or eEF1Bα diverges beyond functionality in the presence of EFL, the system is unable to return to the ancestral, eEF1A:eEFBα-driven state.

The initiation of protein synthesis in bacteria is ruled by three canonical factors: IF1, IF2, and IF3. This system persists in human mitochondria; however, it functions in a rather different way due to specialization and adaptation to the organellar micro-environment. We focused on human mitochondrial IF3, which was earlier studied in vitro, but no knock-out cellular models have been published up to date. In this work, we generated human HeLa cell lines deficient in the MTIF3 gene and analyzed their mitochondrial function. Despite the lack of IF3mt in these cells, they preserved functional mitochondria capable of oxygen consumption and protein synthesis; however, the translation of ATP6 mRNA was selectively decreased which compromised the assembly of ATP synthase. Together with the analogous results obtained earlier for baker's yeast mitochondrial IF3, our findings point to a functional divergence of mitochondrial initiation factors from their bacterial ancestors.

Mitochondria are the organelles of eukaryotic cells responsible for the ATP production by means of the electron transfer chain (ETC). Its work is under strict genetic control providing the correct assembly of the enzyme complexes and the interface to adapt the energetic demands of the cell to the environment. These mechanisms are particularly developed in the cells with high energy consumption, like neurons and myocytes. This review summarizes several aspects of the involvement of the ETC complexes in the transcriptional control mechanisms of the neurons and other cells. Their influence on the differentiation of neurons is also discussed.

Protein biosynthesis in mitochondria is organized in a bacterial manner. However, during evolution, mitochondrial translation mechanisms underwent many organelle-specific changes. In particular, almost all mitochondrial translation factors, being orthologous to bacterial proteins, are characterized by some unique elements of primary or secondary structure. In the case of the organellar initiation factor 3 (IF3), these elements are several dozen amino acids long N- and C-terminal extensions. This study focused on the terminal extensions of baker’s yeast mitochondrial IF3, Aim23p. By in vivo deletion and complementation analysis, we show that at least one extension is necessary for Aim23p function. At the same time, human mitochondrial IF3 is fully functional in yeast mitochondria even without both terminal extensions. While Escherichia coli IF3 itself is poorly active in yeast mitochondria, adding Aim23p terminal extensions makes the resulting chimeric protein as functional as the cognate factor. Our results show that the terminal extensions of IF3 have evolved as the “adaptors” that accommodate the translation factor of bacterial origin to the evolutionary changed protein biosynthesis system in mitochondria.

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Introduction. The article presents the results of studies related to the description of the synthesis and further analysis of the dynamic behavior of unmanned vehicles (UMV) operating in coal-mining pits and other mining quarries. The urgency of the discussed study is dictated by the need to create safe and effective conditions for stripping / mining and transportation operations. This is ensured, among other things, by the operation of unmanned heavy-duty dump cars. Research aim is to develop the concept for the formation of route parameters and models of the movement dynamics of vehicles along technological routes. Methodology. The paper describes the technology for generating and processing the signals in control subsystems as parts of both the computer-aided dispatching system and the on-board autonomous ISSN 0536-1028 «Известия вузов. Горный журнал», № 8, 2020 119 control subsystem of the UMV. The methods used in the research include the study of the forms and characteristics of current trajectories (CT) in relation to a nominal axial trajectory (NAT). In this case, a current trajectory of the UMV is considered within the framework of the so-called S-frames, which are generated in the form of geolocations on a working route of the UMV from the mining face to the place of unloading and vice versa. As a variable characterizing the behavior of the UMV on a current trajectory, a 1D-signal with a time-dependent frequency is adopted, the nature of the change of which is determined by the dynamic shape of a CT with regard to the NAT. Results. Such chirp-signals, together with the wavelet transform apparatus introduced into consideration, allow in a semantically transparent and information-rich video graphic form to represent and subject to further processing the signals characterizing a certain UMV current behavior on the route. The obtained parameters of such secondary wavelet representations of the UMV current dynamics (wavelet maps) are further planned to be used in the subsystem for dynamic modal controlling the UMV movement in the opencast mine. Conclusions. The results of the research allow us to form current routes of UMVs movement according to the models based on the analytical tools accompanying the dynamics of the UMV, proposed in the work.