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  • 1
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    Structure of the 30S translation initiation complex (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-09-02
    Description: Translation initiation, the rate-limiting step of the universal process of protein synthesis, proceeds through sequential, tightly regulated steps. In bacteria, the correct messenger RNA start site and the reading frame are selected when, with the help of initiation factors IF1, IF2 and IF3, the initiation codon is decoded in the peptidyl site of the 30S ribosomal subunit by the fMet-tRNA(fMet) anticodon. This yields a 30S initiation complex (30SIC) that is an intermediate in the formation of the 70S initiation complex (70SIC) that occurs on joining of the 50S ribosomal subunit to the 30SIC and release of the initiation factors. The localization of IF2 in the 30SIC has proved to be difficult so far using biochemical approaches, but could now be addressed using cryo-electron microscopy and advanced particle separation techniques on the basis of three-dimensional statistical analysis. Here we report the direct visualization of a 30SIC containing mRNA, fMet-tRNA(fMet) and initiation factors IF1 and GTP-bound IF2. We demonstrate that the fMet-tRNA(fMet) is held in a characteristic and precise position and conformation by two interactions that contribute to the formation of a stable complex: one involves the transfer RNA decoding stem which is buried in the 30S peptidyl site, and the other occurs between the carboxy-terminal domain of IF2 and the tRNA acceptor end. The structure provides insights into the mechanism of 70SIC assembly and rationalizes the rapid activation of GTP hydrolysis triggered on 30SIC-50S joining by showing that the GTP-binding domain of IF2 would directly face the GTPase-activated centre of the 50S subunit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simonetti, Angelita -- Marzi, Stefano -- Myasnikov, Alexander G -- Fabbretti, Attilio -- Yusupov, Marat -- Gualerzi, Claudio O -- Klaholz, Bruno P -- England -- Nature. 2008 Sep 18;455(7211):416-20. doi: 10.1038/nature07192. Epub 2008 Aug 31.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Genetics and of Molecular and Cellular Biology, Department of Structural Biology and Genomics, Illkirch F-67404, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18758445" target="_blank"〉PubMed〈/a〉
    Keywords: Cryoelectron Microscopy ; Crystallography, X-Ray ; Guanosine Triphosphate/chemistry/metabolism ; Models, Molecular ; Multiprotein Complexes/*chemistry/genetics/metabolism/*ultrastructure ; *Peptide Chain Initiation, Translational ; Prokaryotic Initiation Factor-1/chemistry/genetics/metabolism/ultrastructure ; Prokaryotic Initiation Factor-2/chemistry/genetics/metabolism/ultrastructure ; Protein Conformation ; RNA, Messenger/chemistry/genetics/metabolism ; RNA, Transfer, Met/chemistry/genetics/metabolism/ultrastructure ; Ribosome Subunits/chemistry/metabolism/ultrastructure ; Ribosomes/chemistry/*metabolism/*ultrastructure ; Thermus thermophilus/*enzymology/genetics/*ultrastructure
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Structure of the human 80S ribosome (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-04-23
    Description: Ribosomes are translational machineries that catalyse protein synthesis. Ribosome structures from various species are known at the atomic level, but obtaining the structure of the human ribosome has remained a challenge; efforts to address this would be highly relevant with regard to human diseases. Here we report the near-atomic structure of the human ribosome derived from high-resolution single-particle cryo-electron microscopy and atomic model building. The structure has an average resolution of 3.6 A, reaching 2.9 A resolution in the most stable regions. It provides unprecedented insights into ribosomal RNA entities and amino acid side chains, notably of the transfer RNA binding sites and specific molecular interactions with the exit site tRNA. It reveals atomic details of the subunit interface, which is seen to remodel strongly upon rotational movements of the ribosomal subunits. Furthermore, the structure paves the way for analysing antibiotic side effects and diseases associated with deregulated protein synthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Khatter, Heena -- Myasnikov, Alexander G -- Natchiar, S Kundhavai -- Klaholz, Bruno P -- England -- Nature. 2015 Apr 30;520(7549):640-5. doi: 10.1038/nature14427. Epub 2015 Apr 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, 67404 Illkirch, France [2] Centre National de la Recherche Scientifique (CNRS), UMR 7104, 67404 Illkirch, France [3] Institut National de la Sante et de la Recherche Medicale (INSERM) U964, 67404 Illkirch, France [4] Universite de Strasbourg, 67081 Strasbourg, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25901680" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; *Cryoelectron Microscopy ; Electrons ; Humans ; Models, Molecular ; RNA, Ribosomal/chemistry/metabolism/ultrastructure ; RNA, Transfer/chemistry/metabolism/ultrastructure ; Ribosomal Proteins/chemistry/metabolism/ultrastructure ; Ribosome Subunits/chemistry/metabolism/ultrastructure ; Ribosomes/*chemistry/metabolism/*ultrastructure
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Involvement of protein IF2 N domain in ribosomal subunit joining revealed from architecture and function of the full-length initiation factor (2013)
    National Academy of Sciences
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    Publication Date: 2013-09-12
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 4
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    Ribosomal subunit joining by full-length IF2 [Biochemistry] (2013)
    National Academy of Sciences
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    Publication Date: 2013-09-25
    Description: Translation initiation factor 2 (IF2) promotes 30S initiation complex (IC) formation and 50S subunit joining, which produces the 70S IC. The architecture of full-length IF2, determined by small angle X-ray diffraction and cryo electron microscopy, reveals a more extended conformation of IF2 in solution and on the ribosome than in...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 5
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    Purification, characterization and crystallization of the human 80S ribosome (2014)
    Oxford University Press
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    Publication Date: 2014-04-03
    Description: Ribosomes are key macromolecular protein synthesis machineries in the cell. Human ribosomes have so far not been studied to atomic resolution because of their particularly complex structure as compared with other eukaryotic or prokaryotic ribosomes, and they are difficult to prepare to high homogeneity, which is a key requisite for high-resolution structural work. We established a purification protocol for human 80S ribosomes isolated from HeLa cells that allows obtaining large quantities of homogenous samples as characterized by biophysical methods using analytical ultracentrifugation and multiangle laser light scattering. Samples prepared under different conditions were characterized by direct single particle imaging using cryo electron microscopy, which helped optimizing the preparation protocol. From a small data set, a 3D reconstruction at subnanometric resolution was obtained showing all prominent structural features of the human ribosome, and revealing a salt concentration dependence of the presence of the exit site tRNA, which we show is critical for obtaining crystals. With these well-characterized samples first human 80S ribosome crystals were obtained from several crystallization conditions in capillaries and sitting drops, which diffract to 26 Å resolution at cryo temperatures and for which the crystallographic parameters were determined, paving the way for future high-resolution work.
    Keywords: Ribosomes and Protein Translation
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    Conformation transitions of eukaryotic polyribosomes during multi-round translation (2015)
    Oxford University Press
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    Publication Date: 2015-01-10
    Description: Using sedimentation and cryo electron tomography techniques, the conformations of eukaryotic polyribosomes formed in a long-term cell-free translation system were analyzed over all the active system lifetime (20–30 translation rounds during 6–8 h in wheat germ extract at 25°C). Three distinct types of the conformations were observed: (i) circular polyribosomes, varying from ring-shaped forms to circles collapsed into double rows, (ii) linear polyribosomes, tending to acquire planar zigzag-like forms and (iii) densely packed 3D helices. At the start, during the first two rounds of translation mostly the circular (ring-shaped and double-row) polyribosomes and the linear (free-shaped and zigzag-like) polyribosomes were formed (‘juvenile phase’). The progressive loading of the polyribosomes with translating ribosomes induced the opening of the circular polyribosomes and the transformation of a major part of the linear polyribosomes into the dense 3D helices (‘transitional phase’). After 2 h from the beginning (about 8–10 rounds of translation) this compact form of polyribosomes became predominant, whereas the circular and linear polyribosome fractions together contained less than half of polysomal ribosomes (‘steady-state phase’). The latter proportions did not change for several hours. Functional tests showed a reduced translational activity in the fraction of the 3D helical polyribosomes.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    Formation of circular polyribosomes on eukaryotic mRNA without cap-structure and poly(A)-tail: a cryo electron tomography study (2014)
    Oxford University Press
    Details
    Publication Date: 2014-08-15
    Description: The polyribosomes newly formed on recombinant GFP-encoding mRNAs in a wheat germ cell-free translation system were analyzed using cryo-electron tomography, with sub-tomogram averaging of polysomal ribosomes and reconstruction of 3D structures of individual polyribosomes. The achieved level of resolution in the reconstructed polyribosomes allowed deducing the mRNA path by connecting adjacent exit and entry sites at the ribosomes inside each polyribosome. In this way, the circularity of a significant fraction (about 50%) of translating polyribosomes was proved in the case of the capped poly(A)-tailed mRNA, in agreement with the existing paradigm of the circularization via interaction of cap-bound initiation factor eIF4F with poly(A)-binding protein. However, translation of the capped mRNA construct without poly(A) tail, but with unspecific 3'-UTR derived from non-coding plasmid sequence, also led to the formation of circular polyribosomes in similar proportion (40%). Moreover, the polyribosomes formed on the uncapped non-polyadenylated mRNA with non-synergistic 5'- and 3'-UTRs proved to be circular as well, and appeared in the same proportion as in the previous cases. Thus, the formation of circular polyribosomes was found to be virtually independent of the presence of cap structure and poly(A) tail in mRNA, in contrast to the longstanding paradigm in the field.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 8
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    eIF2B-catalyzed nucleotide exchange and phosphoregulation by the integrated stress response (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉The integrated stress response (ISR) tunes the rate of protein synthesis. Control is exerted by phosphorylation of the general translation initiation factor eIF2. eIF2 is a guanosine triphosphatase that becomes activated by eIF2B, a two-fold symmetric and heterodecameric complex that functions as eIF2’s dedicated nucleotide exchange factor. Phosphorylation converts eIF2 from a substrate into an inhibitor of eIF2B. We report cryo–electron microscopy structures of eIF2 bound to eIF2B in the dephosphorylated state. The structures reveal that the eIF2B decamer is a static platform upon which one or two flexible eIF2 trimers bind and align with eIF2B’s bipartite catalytic centers to catalyze nucleotide exchange. Phosphorylation refolds eIF2α, allowing it to contact eIF2B at a different interface and, we surmise, thereby sequestering it into a nonproductive complex.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Structure of the human TRPM4 ion channel in a lipid nanodisc (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-01-12
    Description: Transient receptor potential (TRP) melastatin 4 (TRPM4) is a widely expressed cation channel associated with a variety of cardiovascular disorders. TRPM4 is activated by increased intracellular calcium in a voltage-dependent manner but, unlike many other TRP channels, is permeable to monovalent cations only. Here we present two structures of full-length human TRPM4 embedded in lipid nanodiscs at ~3-angstrom resolution, as determined by single-particle cryo–electron microscopy. These structures, with and without calcium bound, reveal a general architecture for this major subfamily of TRP channels and a well-defined calcium-binding site within the intracellular side of the S1-S4 domain. The structures correspond to two distinct closed states. Calcium binding induces conformational changes that likely prime the channel for voltage-dependent opening.
    Keywords: Biochemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Dimension in universal algebraic geometry (2014)
    Springer
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    Publication Date: 2014-08-01
    Print ISSN: 1064-5624
    Electronic ISSN: 1531-8362
    Topics: Mathematics
    Published by Springer
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