Alternative conformations and motions adopted by 30S ribosomal subunits visualized by cryo-electron microscopy. 2020

Dushyant Jahagirdar, and Vikash Jha, and Kaustuv Basu, and Josue Gomez-Blanco, and Javier Vargas, and Joaquin Ortega
Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada.

It is only after recent advances in cryo-electron microscopy that it is now possible to describe at high-resolution structures of large macromolecules that do not crystalize. Purified 30S subunits interconvert between an "active" and "inactive" conformation. The active conformation was described by crystallography in the early 2000s, but the structure of the inactive form at high resolution remains unsolved. Here we used cryo-electron microscopy to obtain the structure of the inactive conformation of the 30S subunit to 3.6 Å resolution and study its motions. In the inactive conformation, an alternative base-pairing of three nucleotides causes the region of helix 44, forming the decoding center to adopt an unlatched conformation and the 3' end of the 16S rRNA positions similarly to the mRNA during translation. Incubation of inactive 30S subunits at 42°C reverts these structural changes. The air-water interface to which ribosome subunits are exposed during sample preparation also peel off some ribosomal proteins. Extended exposures to low magnesium concentrations make the ribosomal particles more susceptible to the air-water interface causing the unfolding of large rRNA structural domains. Overall, this study provides new insights about the conformational space explored by the 30S ribosomal subunit when the ribosomal particles are free in solution.

UI MeSH Term Description Entries
D009690 Nucleic Acid Conformation The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape. DNA Conformation,RNA Conformation,Conformation, DNA,Conformation, Nucleic Acid,Conformation, RNA,Conformations, DNA,Conformations, Nucleic Acid,Conformations, RNA,DNA Conformations,Nucleic Acid Conformations,RNA Conformations
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D001483 Base Sequence The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence. DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D012269 Ribosomal Proteins Proteins found in ribosomes. They are believed to have a catalytic function in reconstituting biologically active ribosomal subunits. Proteins, Ribosomal,Ribosomal Protein,Protein, Ribosomal
D012270 Ribosomes Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION. Ribosome
D012336 RNA, Ribosomal, 16S Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis. 16S Ribosomal RNA,16S rRNA,RNA, 16S Ribosomal,Ribosomal RNA, 16S,rRNA, 16S
D054679 Ribosome Subunits, Small The small ribonucleoprotein component of RIBOSOMES. It contains the MESSENGER RNA binding site and two TRANSFER RNA binding sites - one for the incoming AMINO ACYL TRNA (A site) and the other (P site) for the peptidyl tRNA carrying the elongating peptide chain. Ribosomal Subunits, Small,Small Ribosomal Subunits,Small Ribosome Subunits,Ribosomal Subunit, Small,Ribosome Subunit, Small,Small Ribosomal Subunit,Small Ribosome Subunit,Subunit, Small Ribosomal,Subunit, Small Ribosome,Subunits, Small Ribosomal,Subunits, Small Ribosome
D020285 Cryoelectron Microscopy Electron microscopy involving rapid freezing of the samples. The imaging of frozen-hydrated molecules and organelles permits the best possible resolution closest to the living state, free of chemical fixatives or stains. Electron Cryomicroscopy,Cryo-electron Microscopy,Cryo electron Microscopy,Cryo-electron Microscopies,Cryoelectron Microscopies,Cryomicroscopies, Electron,Cryomicroscopy, Electron,Electron Cryomicroscopies,Microscopies, Cryo-electron,Microscopies, Cryoelectron,Microscopy, Cryo-electron,Microscopy, Cryoelectron

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