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Sökning: WFRF:(Amunts Alexey)

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  • Föregående 1[2]3Nästa
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11.
  • Itoh, Yuzuru, et al. (författare)
  • Mechanism of mitoribosomal small subunit biogenesis and preinitiation
  • 2022
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 606, s. 603-608
  • Tidskriftsartikel (refereegranskat)abstract
    • Mitoribosomes are essential for the synthesis and maintenance of bioenergetic proteins. Here we use cryo-electron microscopy to determine a series of the small mitoribosomal subunit (SSU) intermediates in complex with auxiliary factors, revealing a sequential assembly mechanism. The methyltransferase TFB1M binds to partially unfolded rRNA h45 that is promoted by RBFA, while the mRNA channel is blocked. This enables binding of METTL15 that promotes further rRNA maturation and a large conformational change of RBFA. The new conformation allows initiation factor mtIF3 to already occupy the subunit interface during the assembly. Finally, the mitochondria-specific ribosomal protein mS37 (ref. 1) outcompetes RBFA to complete the assembly with the SSU–mS37–mtIF3 complex2 that proceeds towards mtIF2 binding and translation initiation. Our results explain how the action of step-specific factors modulate the dynamic assembly of the SSU, and adaptation of a unique protein, mS37, links the assembly to initiation to establish the catalytic human mitoribosome.
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12.
  • Khawaja, Anas, et al. (författare)
  • Distinct pre-initiation steps in human mitochondrial translation
  • 2020
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Translation initiation in human mitochondria relies upon specialized mitoribosomes and initiation factors, mtIF2 and mtIF3, which have diverged from their bacterial counterparts. Here we report two distinct mitochondrial pre-initiation assembly steps involving those factors. Single-particle cryo-EM revealed that in the first step, interactions between mitochondria-specific protein mS37 and mtIF3 keep the small mitoribosomal subunit in a conformation favorable for a subsequent accommodation of mtIF2 in the second step. Combination with fluorescence cross-correlation spectroscopy analyses suggests that mtIF3 promotes complex assembly without mRNA or initiator tRNA binding, where exclusion is achieved by the N-terminal and C-terminal domains of mtIF3. Finally, the association of large mitoribosomal subunit is required for initiator tRNA and leaderless mRNA recruitment to form a stable initiation complex. These data reveal fundamental aspects of mammalian protein synthesis that are specific to mitochondria.
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13.
  • Kock Flygaard, Rasmus, et al. (författare)
  • Type III ATP synthase is a symmetry-deviated dimer that induces membrane curvature through tetramerization
  • 2020
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Mitochondrial ATP synthases form functional homodimers to induce cristae curvature that is a universal property of mitochondria. To expand on the understanding of this fundamental phenomenon, we characterized the unique type III mitochondrial ATP synthase in its dimeric and tetrameric form. The cryo-EM structure of a ciliate ATP synthase dimer reveals an unusual U-shaped assembly of 81 proteins, including a substoichiometrically bound ATPTT2, 40 lipids, and co-factors NAD and CoQ. A single copy of subunit ATPTT2 functions as a membrane anchor for the dimeric inhibitor IF1. Type III specific linker proteins stably tie the ATP synthase monomers in parallel to each other. The intricate dimer architecture is scaffolded by an extended subunit-a that provides a template for both intra- and inter-dimer interactions. The latter results in the formation of tetramer assemblies, the membrane part of which we determined to 3.1 angstrom resolution. The structure of the type III ATP synthase tetramer and its associated lipids suggests that it is the intact unit propagating the membrane curvature.
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14.
  • Matzov, Donna, et al. (författare)
  • The cryo-EM structure of hibernating 100S ribosome dimer from pathogenic Staphylococcus aureus
  • 2017
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • Formation of 100S ribosome dimer is generally associated with translation suppression in bacteria. Trans-acting factors ribosome modulation factor (RMF) and hibernating promoting factor (HPF) were shown to directly mediate this process in E. coli. Gram-positive S. aureus lacks an RMF homolog and the structural basis for its 100S formation was not known. Here we report the cryo-electron microscopy structure of the native 100S ribosome from S. aureus, revealing the molecular mechanism of its formation. The structure is distinct from previously reported analogs and relies on the HPF C-terminal extension forming the binding platform for the interactions between both of the small ribosomal subunits. The 100S dimer is formed through interactions between rRNA h26, h40, and protein uS2, involving conformational changes of the head as well as surface regions that could potentially prevent RNA polymerase from docking to the ribosome.
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15.
  • Mühleip, Alexander, et al. (författare)
  • ATP synthase hexamer assemblies shape cristae of Toxoplasma mitochondria
  • 2021
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Mitochondrial ATP synthase plays a key role in inducing membrane curvature to establish cristae. In Apicomplexa causing diseases such as malaria and toxoplasmosis, an unusual cristae morphology has been observed, but its structural basis is unknown. Here, we report that the apicomplexan ATP synthase assembles into cyclic hexamers, essential to shape their distinct cristae. Cryo-EM was used to determine the structure of the hexamer, which is held together by interactions between parasite-specific subunits in the lumenal region. Overall, we identified 17 apicomplexan-specific subunits, and a minimal and nuclear-encoded subunit-a. The hexamer consists of three dimers with an extensive dimer interface that includes bound cardiolipins and the inhibitor IF1. Cryo-ET and subtomogram averaging revealed that hexamers arrange into ~20-megadalton pentagonal pyramids in the curved apical membrane regions. Knockout of the linker protein ATPTG11 resulted in the loss of pentagonal pyramids with concomitant aberrantly shaped cristae. Together, this demonstrates that the unique macromolecular arrangement is critical for the maintenance of cristae morphology in Apicomplexa.
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16.
  • Mühleip, Alexander, et al. (författare)
  • Structure of a mitochondrial ATP synthase with bound native cardiolipin
  • 2019
  • Ingår i: eLIFE. - 2050-084X. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • The mitochondrial ATP synthase fuels eukaryotic cells with chemical energy. Here we report the cryo-EM structure of a divergent ATP synthase dimer from mitochondria of Euglena gracilis, a member of the phylum Euglenozoa that also includes human parasites. It features 29 different subunits, 8 of which are newly identified. The membrane region was determined to 2.8 angstrom resolution, enabling the identification of 37 associated lipids, including 25 cardiolipins, which provides insight into protein-lipid interactions and their functional roles. The rotor-stator interface comprises four membrane-embedded horizontal helices, including a distinct subunit a. The dimer interface is formed entirely by phylum-specific components, and a peripherally associated subcomplex contributes to the membrane curvature. The central and peripheral stalks directly interact with each other. Last, the ATPase inhibitory factor 1 (IF1) binds in a mode that is different from human, but conserved in Trypanosomatids.
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17.
  • Nirwan, Neha, et al. (författare)
  • Structure-based mechanism for activation of the AAA plus GTPase McrB by the endonuclease McrC
  • 2019
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • The AAA+ GTPase McrB powers DNA cleavage by the endonuclease McrC. The GTPase itself is activated by McrC. The architecture of the GTPase and nuclease complex, and the mechanism of their activation remained unknown. Here, we report a 3.6 angstrom structure of a GTPase-active and DNA-binding deficient construct of McrBC. Two hexameric rings of McrB are bridged by McrC dimer. McrC interacts asymmetrically with McrB protomers and inserts a stalk into the pore of the ring, reminiscent of the gamma subunit complexed to alpha(3)beta(3) of F-1-ATPase. Activation of the GTPase involves conformational changes of residues essential for hydrolysis. Three consecutive nucleotide-binding pockets are occupied by the GTP analogue 5'-guanylyl imidodiphosphate and the next three by GDP, which is suggestive of sequential GTP hydrolysis.
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18.
  • Ott, Martin, et al. (författare)
  • Organization and Regulation of Mitochondrial Protein Synthesis
  • 2016
  • Ingår i: Annual Review of Biochemistry. - 0066-4154 .- 1545-4509. ; 85, s. 77-101
  • Forskningsöversikt (refereegranskat)abstract
    • Mitochondria are essential organelles of endosymbiotic origin that are responsible for oxidative phosphorylation within eukaryotic cells. Independent evolution between species has generated mitochondrial genomes that are extremely diverse, with the composition of the vestigial genome determining their translational requirements. Typically, translation within mitochondria is restricted to a few key subunits of the oxidative phosphorylation complexes that are synthesized by dedicated ribosomes (mitoribosomes). The dramatically rearranged mitochondrial genomes, the limited set of transcripts, and the need for the synthesized proteins to coassemble with nuclear-encoded subunits have had substantial consequences for the translation machinery. Recent high-resolution cryo-electron microscopy has revealed the effect of coevolution on the mitoribosome with the mitochondrial genome. In this review, we place the new structural information in the context of the molecular mechanisms of mitochondrial translation and focus on the novel ways protein synthesis is organized and regulated in mitochondria.
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19.
  • Perez Boerema, Annemarie, 1991- (författare)
  • Cryo-EM Studies of Macromolecular Complexes from Photosynthetic Organisms
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Plants, algae, and cyanobacteria convert light energy into chemical energy through the process of photosynthesis, fueling the planet and making life as we know it possible. Photosystem I (PSI) is one of the main photosynthetic complexes, responsible for this process. PSI uses the energy of light to transfer electrons from the soluble electron carrier plastocyanin, on the lumenal site of the thylakoid membrane, to ferrodoxin, on the stromal site of the membrane. Thus, playing a key role in the light dependent reactions. In order to survive many photosynthetic organisms need to be able to adapt to fluctuations in light and have adapted their photosynthetic machinery accordingly. In recent years many advances have been made in electron cryo-microscopy, making it possible to visualize many previously elusive photosynthetic complexes. This has brought a wealth of information on the structural adaptations of PSI.In plants and algae, PSI is hosted by the chloroplast, a specialized organelle that houses the photosynthetic reactions. In the chloroplast, key components of PSI are synthesized by the chloroplasts own translation machinery: the chloroplast ribosome. Translation in the chloroplast is remarkable as it has to synchronize translation in two different genetic compartments as well as adapt to fluctuations in light. A glimpse of how this machinery has evolved to be able to fulfill all of these duties can be obtained from its three dimensional structure and its chloroplast specific features. However, despite all this structural information providing valuable clues as to the functioning of these systems, there are still many aspects of how they play a role that still remain unknown.
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20.
  • Perez-Boerema, Annemarie, et al. (författare)
  • Structure of a minimal photosystem I from the green alga Dunaliella salina
  • 2020
  • Ingår i: Nature plants. - 2055-026X .- 2055-0278. ; 6:3, s. 321-327
  • Tidskriftsartikel (refereegranskat)abstract
    • Solar energy harnessed by oxygenic photosynthesis supports most of the life forms on Earth. In eukaryotes, photosynthesis occurs in chloroplasts and is achieved by membrane-embedded macromolecular complexes that contain core and peripheral antennae with multiple pigments. The structure of photosystem I (PSI) comprises the core and light-harvesting (LHCI) complexes, which together form PSI-LHCI. Here we determined the structure of PSI-LHCI from the salt-tolerant green alga Dunaliella salina using X-ray crystallography and electron cryo-microscopy. Our results reveal a previously undescribed configuration of the PSI core. It is composed of only 7 subunits, compared with 14-16 subunits in plants and the alga Chlamydomonas reinhardtii, and forms the smallest known PSI. The LHCI is poorly conserved at the sequence level and binds to pigments that form new energy pathways, and the interactions between the individual Lhca1-4 proteins are weakened. Overall, the data indicate the PSI of D. salina represents a different type of the molecular organization that provides important information for reconstructing the plasticity and evolution of PSI. The photosystem I light-harvesting complex from the salt-tolerant green alga Dunaliella salina has a core configuration composed of only seven subunits. This unusual molecular organization could inform the reconstruction of photosystem evolution.
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  • Resultat 11-20 av 30
  • Föregående 1[2]3Nästa

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