Function of the ribosomal E-site: a mutagenesis study

Ribosomes synthesize proteins according to the information encoded in mRNA. During this process, both the incoming amino acid and the nascent peptide are bound to tRNA molecules. Three binding sites for tRNA in the ribosome are known: the A-site for aminoacyl-tRNA, the P-site for peptidyl-tRNA and the E-site for the deacylated tRNA leaving the ribosome. Here, we present a study of Escherichia coli ribosomes with the E-site binding destabilized by mutation C2394G of the 23S rRNA. Expression of the mutant 23S rRNA in vivo caused increased frameshifting and stop codon readthrough. The progression of these ribosomes through the ribosomal elongation cycle in vitro reveals ejection of deacylated tRNA during the translocation step or shortly after. E-site compromised ribosomes can undergo translocation, although in some cases it is less efficient and results in a frameshift. The mutation affects formation of the P/E hybrid site and leads to a loss of stimulation of the multiple turnover GTPase activity of EF-G by deacylated tRNA bound to the ribosome

Non-financial motivation practices: Megafon and Nestle

The article examines factors which influence the effectiveness of employee motivation, as well as presents the main aspects that need to be taken into account to develop the optimal system of financial and non-financial motivation of employees in international companies. At the same time, a comparative analysis of existing employee motivation practices is provided, using the example of two giant companies: Megafon and Nestle

Chemical shift assignments and the secondary structure of the Est3 telomerase subunit in the yeast Hansenula polymorpha

© 2017 Springer Science+Business Media B.V. Telomerase is a multisubunit ribonucleoprotein enzyme that is essential for continuous cellular proliferation. A key role of telomerase in cancer and ageing makes it a promising target for the development of cancer therapies and treatments of other age-associated diseases, since telomerase allows unlimited proliferation potential of cells in the majority of cancer types. However, the structure and molecular mechanism of telomerase action are still poorly understood. In budding yeast, telomerase consists of the catalytic subunit, the telomerase reverse transcriptase or Est2 protein, telomerase RNA (TLC1) and two regulatory subunits, Est1 and Est3. Each of the four subunits is essential for in vivo telomerase function. Est3 interacts directly with Est1 and Est2, and stimulates Est2 catalytic activity. However, the exact role of the Est3 protein in telomerase function is still unknown. Determination of the structure, dynamic and functional properties of Est3 can bring new insights into the molecular mechanism of telomerase activity. Here we report nearly complete 1 H, 13 C and 15 N resonance assignments of Est3 from the yeast Hansenula polymorpha. Analysis of the assigned chemical shifts allowed us to identify the protein’s secondary structure and backbone dynamic properties. Structure-based sequence alignment revealed similarities in the structural organization of yeast Est3 and mammalian TPP1 proteins

The structure of helix 89 of 23S rRNA is important for peptidyl transferase function of Escherichia coli ribosome

AbstractHelix 89 of the 23S rRNA connects ribosomal peptidyltransferase center and elongation factor binding site. Secondary structure of helix 89 determined by X-ray structural analysis involves less base pairs then could be drawn for the helix of the same primary structure. It can be that alternative secondary structure might be realized at some stage of translation. Here by means of site-directed mutagenesis we stabilized either the “X-ray” structure or the structure with largest number of paired nucleotides. Mutation UU2492-3C which aimed to provide maximal pairing of the helix 89 of the 23S rRNA was lethal. Mutant ribosomes were unable to catalyze peptide transfer independently either with aminoacyl-tRNA or puromycin

Specific features of telomerase RNA from Hansenula polymorpha.

Telomerase, a ribonucleoprotein, is responsible for the maintenance of eukaryotic genome integrity by replicating the ends of chromosomes. The core enzyme comprises the conserved protein TERT and an RNA subunit (TER) that, in contrast, displays large variations in size and structure. Here, we report the identification of the telomerase RNA from thermotolerant yeast Hansenula polymorpha (HpTER) and describe its structural features. We show further that the H. polymorpha telomerase reverse transcribes the template beyond the predicted boundary and adds a nontelomeric dT in vitro. Sequencing of the chromosomal ends revealed that this nucleotide is specifically present as a terminal nucleotide at the 3' end of telomeres. Mutational analysis of HpTER confirmed that the incorporation of dT functions to limit telomere length in this species

Acid-basic and sorption characteristics of tungsten-containing materials based on saponite clay

Целью данной работы было выявить влияние модификации на кислотно-основные характеристики сапонитовой природной глины и глины, модифицированной магнетитом