Multifaceted Mechanism of Amicoumacin A Inhibition of Bacterial Translation

Amicoumacin A (Ami) halts bacterial growth by inhibiting the ribosome during translation. The Ami binding site locates in the vicinity of the E-site codon of mRNA. However, Ami does not clash with mRNA, rather stabilizes it, which is relatively unusual and implies a unique way of translation inhibition. In this work, we performed a kinetic and thermodynamic investigation of Ami influence on the main steps of polypeptide synthesis. We show that Ami reduces the rate of the functional canonical 70S initiation complex (IC) formation by 30-fold. Additionally, our results indicate that Ami promotes the formation of erroneous 30S ICs; however, IF3 prevents them from progressing towards translation initiation. During early elongation steps, Ami does not compromise EF-Tu-dependent A-site binding or peptide bond formation. On the other hand, Ami reduces the rate of peptidyl-tRNA movement from the A to the P site and significantly decreases the amount of the ribosomes capable of polypeptide synthesis. Our data indicate that Ami progressively decreases the activity of translating ribosomes that may appear to be the main inhibitory mechanism of Ami. Indeed, the use of EF-G mutants that confer resistance to Ami (G542V, G581A, or ins544V) leads to a complete restoration of the ribosome functionality. It is possible that the changes in translocation induced by EF-G mutants compensate for the activity loss caused by Ami.Russian Foundation for Basic ResearchRevisión por pare

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

Signs and Symptoms of Central Nervous System Involvement and Their Pathogenesis in COVID-19 According to The Clinical Data (Review)

Detailed clinical assessment of the central nervous system involvement in SARS-CoV-2 infection is relevant due to the low specificity of neurological manifestations, the complexity of evaluation of patient complaints, reduced awareness of the existing spectrum of neurological manifestations of COVID-19, as well as low yield of the neurological imaging.The aim. To reveal the patterns of central nervous system involvement in COVID-19 and its pathogenesis based on clinical data.Among more than 200 primary literature sources from various databases (Scopus, Web of Science, RSCI, etc.), 80 sources were selected for evaluation, of them 72 were published in the recent years (2016-2020). The criteria for exclusion of sources were low relevance and outdated information.The clinical manifestations of central nervous system involvement in COVID-19 include smell (5-98% of cases) and taste disorders (6-89%), dysphonia (28%), dysphagia (19%), consciousness disorders (3-53%), headache (0-70%), dizziness (0-20%), and, in less than 3% of cases, visual impairment, hearing impairment, ataxia, seizures, stroke. Analysis of the literature data revealed the following significant mechanisms of the effects of highly contagious coronaviruses (including SARS-CoV-2) on the central nervous system: neurodegeneration (including cytokine- induced); cerebral thrombosis and thromboembolism; damage to the neurovascular unit; immune-mediated damage of nervous tissue, resulting in infection and allergy-induced demyelination.The neurological signs and symptoms seen in COVID-19 such as headache, dizziness, impaired smell and taste, altered level of consciousness, bulbar disorders (dysphagia, dysphonia) have been examined. Accordingly, we discussed the possible routes of SARS-CoV-2 entry into the central nervous system and the mechanisms of nervous tissue damage.Based on the literature analysis, a high frequency and variability of central nervous system manifestations of COVID-19 were revealed, and an important role of vascular brain damage and neurodegeneration in the pathogenesis of COVID-19 was highlighted

Особенности симптоматики и патогенеза повреждения центральной нервной системы при COVID-19 по данным клинических исследований (обзор)

Detailed clinical assessment of the central nervous system involvement in SARS-CoV-2 infection is relevant due to the low specificity of neurological manifestations, the complexity of evaluation of patient complaints, reduced awareness of the existing spectrum of neurological manifestations of COVID-19, as well as low yield of the neurological imaging.The aim. To reveal the patterns of central nervous system involvement in COVID-19 and its pathogenesis based on clinical data.Among more than 200 primary literature sources from various databases (Scopus, Web of Science, RSCI, etc.), 80 sources were selected for evaluation, of them 72 were published in the recent years (2016-2020). The criteria for exclusion of sources were low relevance and outdated information.The clinical manifestations of central nervous system involvement in COVID-19 include smell (5-98% of cases) and taste disorders (6-89%), dysphonia (28%), dysphagia (19%), consciousness disorders (3-53%), headache (0-70%), dizziness (0-20%), and, in less than 3% of cases, visual impairment, hearing impairment, ataxia, seizures, stroke. Analysis of the literature data revealed the following significant mechanisms of the effects of highly contagious coronaviruses (including SARS-CoV-2) on the central nervous system: neurodegeneration (including cytokine- induced); cerebral thrombosis and thromboembolism; damage to the neurovascular unit; immune-mediated damage of nervous tissue, resulting in infection and allergy-induced demyelination.The neurological signs and symptoms seen in COVID-19 such as headache, dizziness, impaired smell and taste, altered level of consciousness, bulbar disorders (dysphagia, dysphonia) have been examined. Accordingly, we discussed the possible routes of SARS-CoV-2 entry into the central nervous system and the mechanisms of nervous tissue damage.Based on the literature analysis, a high frequency and variability of central nervous system manifestations of COVID-19 were revealed, and an important role of vascular brain damage and neurodegeneration in the pathogenesis of COVID-19 was highlighted.Актуальность пристальной клинической оценки поражения центральной нервной системы вирусом SARS-CoV-2 определяется низкой специфичностью ряда неврологических симптомов, сложностью объективизации жалоб пациента, неоднородной осведомленностью и настороженностью по поводу имеющегося спектра неврологических симптомов COVID-19, низкой частотой патологических изменений по данным нейровизуализации.Цель обзора. Выявление особенностей симптоматики и патогенеза поражения центральной нервной системы при COVID-19 на основе анализа данных клинической практики.Из более 200 первично отобранных источников литературы различных баз данных (Scopus, Web of science, РИНЦ и др.) для анализа выбрали 80 источников, из них — 72 источника, опубликованных в течение последних лет (2016-2020 гг.). Критерием исключения источников служили малая информативность и устаревшие данные.Клиническая картина поражения центральной нервной системы при COVID-19 включает в себя: нарушение обоняния (5-98% случаев), нарушение вкусовой чувствительности (6-89%), дисфонию (28%), дисфагию (19%), количественные и качественные нарушения сознания (3-53%), головную боль (0-70%), головокружение (0-20%), менее 3% случаев — нарушение зрения, слуха, атаксию, судорожный приступ, инсульт. Анализ данных литературы позволил выделить следующие значимые механизмы воздействия высококонтагиозных коронавирусов (в том числе вируса SARS-CoV-2) на центральную нервную систему: нейродегенерация (в том числе цитокининдуцированная); церебральный тромбоз и церебральная тромбоэмболия; повреждение нейрососудистой единицы; иммуноопосредованное поражение нервной ткани, приводящее к развитию инфекционно-аллергического демие-линизирующего процесса.Рассмотрели симптомы поражения нервной системы при COVID-19, такие как головная боль, головокружение, нарушение обоняния и вкусовых ощущений, изменение уровня сознания, бульбарные нарушения (дисфагия, дисфония). Соответственно, проанализировали данные о возможных путях проникновения SARS-CoV-2 в центральную нервную систему и механизмы поражения нервной ткани.По результатам проведенного анализа отечественной и зарубежной литературы показали высокую частоту и полиморфность симптомов поражения центральной нервной системы, а также важную роль сосудистого поражения головного мозга и нейродегенерации в патогенезе COVID-19

Structure-Function Analysis of Human TYW2 Enzyme Required for the Biosynthesis of a Highly Modified Wybutosine (yW) Base in Phenylalanine-tRNA

Posttranscriptional modifications are critical for structure and function of tRNAs. Wybutosine (yW) and its derivatives are hyper-modified guanosines found at the position 37 of eukaryotic and archaeal tRNAPhe. TYW2 is an enzyme that catalyzes α-amino-α-carboxypropyl transfer activity at the third step of yW biogenesis. Using complementation of a ΔTYW2 strain, we demonstrate here that human TYW2 (hTYW2) is active in yeast and can synthesize the yW of yeast tRNAPhe. Structure-guided analysis identified several conserved residues in hTYW2 that interact with S-adenosyl-methionine (AdoMet), and mutation studies revealed that K225 and E265 are critical residues for the enzymatic activity. We previously reported that the human TYW2 is overexpressed in breast cancer. However, no difference in the tRNAPhe modification status was observed in either normal mouse tissue or a mouse tumor model that overexpresses Tyw2, indicating that hTYW2 may have a role in tumorigenesis unrelated to yW biogenesis