scholarly journals The initiation of protein synthesis: joining of the 50S ribosomal subunit to the initiation complex.

1967 ◽  
Vol 58 (4) ◽  
pp. 1487-1493 ◽  
Author(s):  
M. Nomura ◽  
C. V. Lowry ◽  
C. Guthrie
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Subunit ◽  
Initiation Complex

scholarly journals The Oxazolidinone Linezolid Inhibits Initiation of Protein Synthesis in Bacteria

1998 ◽  
Vol 42 (12) ◽  
pp. 3251-3255 ◽  
Author(s):  
Steve M. Swaney ◽  
Hiroyuki Aoki ◽  
M. Clelia Ganoza ◽  
Dean L. Shinabarger
Keyword(s):  
Protein Synthesis ◽  
Complex Formation ◽  
Antimicrobial Agents ◽  
Ribosomal Subunit ◽  
Multidrug Resistant ◽  
Binary Complex ◽  
Initiation Complex ◽  
Ribosomal Subunits ◽  
Bacterial Translation

ABSTRACT The oxazolidinones represent a new class of antimicrobial agents which are active against multidrug-resistant staphylococci, streptococci, and enterococci. Previous studies have demonstrated that oxazolidinones inhibit bacterial translation in vitro at a step preceding elongation but after the charging ofN-formylmethionine to the initiator tRNA molecule. The event that occurs between these two steps is termed initiation. Initiation of protein synthesis requires the simultaneous presence of N-formylmethionine-tRNA, the 30S ribosomal subunit, mRNA, GTP, and the initiation factors IF1, IF2, and IF3. An initiation complex assay measuring the binding of [3H]N-formylmethionyl-tRNA to ribosomes in response to mRNA binding was used in order to investigate the mechanism of oxazolidinone action. Linezolid inhibited initiation complex formation with either the 30S or the 70S ribosomal subunits fromEscherichia coli. In addition, complex formation withStaphylococcus aureus 70S tight-couple ribosomes was inhibited by linezolid. Linezolid did not inhibit the independent binding of either mRNA or N-formylmethionyl-tRNA toE. coli 30S ribosomal subunits, nor did it prevent the formation of the IF2–N-formylmethionyl-tRNA binary complex. The results demonstrate that oxazolidinones inhibit the formation of the initiation complex in bacterial translation systems by preventing formation of theN-formylmethionyl-tRNA–ribosome–mRNA ternary complex.

scholarly journals Inhibition of translation initiation complex formation by GE81112 unravels a 16S rRNA structural switch involved in P-site decoding

2016 ◽  
Vol 113 (16) ◽  
pp. E2286-E2295 ◽  
Author(s):  
Attilio Fabbretti ◽  
Andreas Schedlbauer ◽  
Letizia Brandi ◽  
Tatsuya Kaminishi ◽  
Anna Maria Giuliodori ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Translation Initiation ◽  
Dynamic Equilibrium ◽  
Ribosomal Subunit ◽  
Structural Level ◽  
Initiation Complex ◽  
Stem Loop ◽  
Initiation Factors ◽  
Initiation Phase

In prokaryotic systems, the initiation phase of protein synthesis is governed by the presence of initiation factors that guide the transition of the small ribosomal subunit (30S) from an unlocked preinitiation complex (30S preIC) to a locked initiation complex (30SIC) upon the formation of a correct codon–anticodon interaction in the peptidyl (P) site. Biochemical and structural characterization of GE81112, a translational inhibitor specific for the initiation phase, indicates that the main mechanism of action of this antibiotic is to prevent P-site decoding by stabilizing the anticodon stem loop of the initiator tRNA in a distorted conformation. This distortion stalls initiation in the unlocked 30S preIC state characterized by tighter IF3 binding and a reduced association rate for the 50S subunit. At the structural level we observe that in the presence of GE81112 the h44/h45/h24a interface, which is part of the IF3 binding site and forms ribosomal intersubunit bridges, preferentially adopts a disengaged conformation. Accordingly, the findings reveal that the dynamic equilibrium between the disengaged and engaged conformations of the h44/h45/h24a interface regulates the progression of protein synthesis, acting as a molecular switch that senses and couples the 30S P-site decoding step of translation initiation to the transition from an unlocked preIC to a locked 30SIC state.

scholarly journals Interaction between membrane functions and protein synthesis in reticulocytes. An elongation-stage inhibitor of protein synthesis extracted from the reticulocyte membrane

1979 ◽  
Vol 180 (2) ◽  
pp. 379-387 ◽  
Author(s):  
D H Wreschner ◽  
M Herzberg
Keyword(s):  
Protein Synthesis ◽  
Cell Membrane ◽  
High Speed ◽  
Ribosomal Subunit ◽  
Initiation Factor ◽  
Membrane Component ◽  
Initiation Complex ◽  
Initiation Factor 2 ◽  
Reticulocyte Lysate ◽  
Inhibitor Of Protein Synthesis

A component of the reticulocyte cell membrane was found to inhibit protein synthesis severely in a reticulocyte lysate system. An investigation into the mode of action of the membrane inhibitor revealed the following facts. (1) The binding of the tertiary initiation complex (methionyl-tRNAfMet-Initiation Factor 2-GTP) to the 40S ribosomal subunit was unaffected by the membrane inhibitor. (2) The membrane component did not interfere with the binding of the 40S initiation complex to the AUG initiation codon and subsequent attachment of the 60S ribosomal subunit. (3) Elongation of the peptide chain, as assayed by peptidyl-puromycin formation, was markedly affected by the membrane inhibitor. Surprisingly, the membrane component caused a considerable increase in peptidyl-puromycin formation. (4) Reticulocyte ribosomes that had been reisolated by high-speed centrifugation, after preincubation with the membrane component, were found to be highly defective when assayed in a cell-free protein-synthesizing system. These results indicated that an extract of the reticulocyte cell membrane inhibited protein synthesis by interacting with the ribosome and thus interfered with the correct functions of the elongation stage of protein synthesis. The implications of this conclusion are discussed in the light of data showing that a highly purified preparation of the membrane inhibitor also displayed an endonucleolytic activity highly specific for 28S RNA.

scholarly journals Tagging of RPS9 as a tool for ribosome purification and identification of ribosome-associated proteins

2020 ◽  
pp. 57-57
Author(s):  
Bogdan Jovanovic ◽  
Lisa Schubert ◽  
Fabian Poetz ◽  
Georg Stoecklin
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Proteins ◽  
Associated Factors ◽  
Ribosomal Subunit ◽  
High Specificity ◽  
Negative Control ◽  
Tev Protease ◽  
Protease Cleavage ◽  
Associated Proteins ◽  
And Function

Ribosomes, the catalytic machinery required for protein synthesis, are comprised of 4 ribosomal RNAs and about 80 ribosomal proteins in mammals. Ribosomes further interact with numerous associated factors that regulate their biogenesis and function. As mutations of ribosomal proteins and ribosome associated proteins cause many diseases, it is important to develop tools by which ribosomes can be purified efficiently and with high specificity. Here, we designed a method to purify ribosomes from human cell lines by C-terminally tagging human RPS9, a protein of the small ribosomal subunit. The tag consists of a flag peptide and a streptavidin-binding peptide (SBP) separated by the tobacco etch virus (TEV) protease cleavage site. We demonstrate that RPS9-Flag-TEV-SBP (FTS) is efficiently incorporated into the ribosome without interfering with regular protein synthesis. Using HeLa-GFP-G3BP1 cells stably expressing RPS9-FTS or, as a negative control, mCherry-FTS, we show that complete ribosomes as well as numerous ribosome-associated proteins are efficiently and specifically purified following pull-down of RPS9-FTS using streptavidin beads. This tool will be helpful for the characterization of human ribosome heterogeneity, post-translational modifications of ribosomal proteins, and changes in ribosome-associated factors after exposing human cells to different stimuli and conditions.

scholarly journals A Complementary Mechanism of Bacterial mRNA Translation Inhibition by Tetracyclines

2021 ◽  
Vol 12 ◽  
Author(s):  
Victor Barrenechea ◽  
Maryhory Vargas-Reyes ◽  
Miguel Quiliano ◽  
Pohl Milón
Keyword(s):  
Protein Synthesis ◽  
Translation Initiation ◽  
Ribosomal Subunit ◽  
Mrna Translation ◽  
Resistance Mechanisms ◽  
Dissociation Rate ◽  
Initiation Factor ◽  
Translation Elongation ◽  
Initiation Phase ◽  
Complementary Mechanism

Tetracycline has positively impacted human health as well as the farming and animal industries. Its extensive usage and versatility led to the spread of resistance mechanisms followed by the development of new variants of the antibiotic. Tetracyclines inhibit bacterial growth by impeding the binding of elongator tRNAs to the ribosome. However, a small number of reports indicated that Tetracyclines could also inhibit translation initiation, yet the molecular mechanism remained unknown. Here, we use biochemical and computational methods to study how Oxytetracycline (Otc), Demeclocycline (Dem), and Tigecycline (Tig) affect the translation initiation phase of protein synthesis. Our results show that all three Tetracyclines induce Initiation Factor IF3 to adopt a compact conformation on the 30S ribosomal subunit, similar to that induced by Initiation Factor IF1. This compaction was faster for Tig than Dem or Otc. Furthermore, all three tested tetracyclines affected IF1-bound 30S complexes. The dissociation rate constant of IF1 in early 30S complexes was 14-fold slower for Tig than Dem or Otc. Late 30S initiation complexes (30S pre-IC or IC) exhibited greater IF1 stabilization by Tig than for Dem and Otc. Tig and Otc delayed 50S joining to 30S initiation complexes (30S ICs). Remarkably, the presence of Tig considerably slowed the progression to translation elongation and retained IF1 in the resulting 70S initiation complex (70S IC). Molecular modeling of Tetracyclines bound to the 30S pre-IC and 30S IC indicated that the antibiotics binding site topography fluctuates along the initiation pathway. Mainly, 30S complexes show potential contacts between Dem or Tig with IF1, providing a structural rationale for the enhanced affinity of the antibiotics in the presence of the factor. Altogether, our data indicate that Tetracyclines inhibit translation initiation by allosterically perturbing the IF3 layout on the 30S, retaining IF1 during 70S IC formation, and slowing the transition toward translation elongation. Thus, this study describes a new complementary mechanism by which Tetracyclines may inhibit bacterial protein synthesis.

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