| 1. |
- Hällberg, B Martin, et al.
(författare)
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TFAM forces mtDNA to make a U-turn
- 2011
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Ingår i: Nature Structural and Molecular Biology. - Stockholm : Karolinska Institutet, Dept of Cell and Molecular Biology. - 1545-9993 .- 1545-9985.
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Tidskriftsartikel (refereegranskat)abstract
- The mammalian mitochondrial transcription factor A (TFAM) is encoded in the nucleus and imported into mitochondria, where it functions as an activator of mtDNA transcription and packages mtDNA into DNA-protein aggregates called mitochondrial nucleoids. Two X-ray crystallography studies in this issue reveal that TFAM shapes mtDNA into a sharp U-turn, thereby providing a molecular mechanism for its dual roles in the expression and maintenance of mtDNA.
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| 2. |
- Larsson, Anton J M, et al.
(författare)
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X-chromosome upregulation is driven by increased burst frequency
- 2019
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Ingår i: Nature Structural & Molecular Biology. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 1545-9993 .- 1545-9985.
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Tidskriftsartikel (refereegranskat)abstract
- Ohno's hypothesis postulates that X-chromosome upregulation rectifies X-dose imbalance relative to autosomal genes, present in two active copies per cell. Here we dissected X-upregulation into kinetics of transcription, inferred from allele-specific single-cell RNA-sequencing (scRNAseq) data from somatic mouse cells. We confirmed increased X-chromosome expression in female and male somatic cells, and remarkably found that the X-chromosome achieved upregulation by elevated burst frequencies. By monitoring differentiating female embryonic stem cells, we found that elevated burst frequency established on the active X-chromosome as X-inactivation occurred on the other allele. This provides mechanistic insights into X-chromosome upregulation.
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| 3. |
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| 4. |
- Akke, Mikael
(författare)
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Out of hot water
- 2004
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 11:10, s. 912-913
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Tidskriftsartikel (refereegranskat)abstract
- A recent study of adenylate kinase reveals that conformational dynamics in control product release and determine the rate-limiting step in the overall catalytic reaction.
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| 5. |
- Ameur, Adam, et al.
(författare)
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Total RNA sequencing reveals nascent transcription and widespread co-transcriptional splicing in the human brain
- 2011
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 18:12, s. 1435-1440
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Tidskriftsartikel (refereegranskat)abstract
- Transcriptome sequencing allows for analysis of mature RNAs at base pair resolution. Here we show that RNA-seq can also be used for studying nascent RNAs undergoing transcription. We sequenced total RNA from human brain and liver and found a large fraction of reads (up to 40%) within introns. Intronic RNAs were abundant in brain tissue, particularly for genes involved in axonal growth and synaptic transmission. Moreover, we detected significant differences in intronic RNA levels between fetal and adult brains. We show that the pattern of intronic sequence read coverage is explained by nascent transcription in combination with co-transcriptional splicing. Further analysis of co-transcriptional splicing indicates a correlation between slowly removed introns and alternative splicing. Our data show that sequencing of total RNA provides unique insight into the transcriptional processes in the cell, with particular importance for normal brain development.
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| 6. |
- Anandapadmanaban, Madhanagopal, et al.
(författare)
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High-resolution structure of TBP with TAF1 reveals anchoring patterns in transcriptional regulation
- 2013
-
Ingår i: Nature Structural & Molecular Biology. - : NATURE PUBLISHING GROUP, 75 VARICK ST, 9TH FLR, NEW YORK, NY 10013-1917 USA. - 1545-9993 .- 1545-9985. ; 20:8, s. 1008-
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Tidskriftsartikel (refereegranskat)abstract
- The general transcription factor TFIID provides a regulatory platform for transcription initiation. Here we present the crystal structure (1.97 angstrom) and NMR analysis of yeast TAF1 N-terminal domains TAND1 and TAND2 bound to yeast TBP, together with mutational data. We find that yeast TAF1-TAND1, which in itself acts as a transcriptional activator, binds TBPs concave DNA-binding surface by presenting similar anchor residues to TBP as does Mot1 but from a distinct structural scaffold. Furthermore, we show how TAF1-TAND2 uses an aromatic and acidic anchoring pattern to bind a conserved TBP surface groove traversing the basic helix region, and we find highly similar TBP-binding motifs also presented by the structurally distinct TFIIA, Mot1 and Brf1 proteins. Our identification of these anchoring patterns, which can be easily disrupted or enhanced, provides insight into the competitive multiprotein TBP interplay critical to transcriptional regulation.
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| 7. |
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| 8. |
- Asami, Jinta, et al.
(författare)
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Structural basis of hepatitis B virus receptor binding
- 2024
-
Ingår i: Nature Structural & Molecular Biology. - 1545-9993 .- 1545-9985. ; 31, s. 447-454
-
Tidskriftsartikel (refereegranskat)abstract
- Hepatitis B virus (HBV), a leading cause of developing hepatocellular carcinoma affecting more than 290 million people worldwide, is an enveloped DNA virus specifically infecting hepatocytes. Myristoylated preS1 domain of the HBV large surface protein binds to the host receptor sodium-taurocholate cotransporting polypeptide (NTCP), a hepatocellular bile acid transporter, to initiate viral entry. Here, we report the cryogenic-electron microscopy structure of the myristoylated preS1 (residues 2–48) peptide bound to human NTCP. The unexpectedly folded N-terminal half of the peptide embeds deeply into the outward-facing tunnel of NTCP, whereas the C-terminal half formed extensive contacts on the extracellular surface. Our findings reveal an unprecedented induced-fit mechanism for establishing high-affinity virus–host attachment and provide a blueprint for the rational design of anti-HBV drugs targeting virus entry.
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| 9. |
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| 10. |
- Banci, L, et al.
(författare)
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Structural proteomics: from the molecule to the system
- 2007
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Ingår i: Nature structural & molecular biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 14:1, s. 3-4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 11. |
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| 12. |
- Bibow, Stefan, et al.
(författare)
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Solution structure of discoidal high-density lipoprotein particles with a shortened apolipoprotein A-I.
- 2017
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 24:2, s. 187-193
-
Tidskriftsartikel (refereegranskat)abstract
- High-density lipoprotein (HDL) particles are cholesterol and lipid transport containers. Mature HDL particles destined for the liver develop through the formation of intermediate discoidal HDL particles, which are the primary acceptors for cholesterol. Here we present the three-dimensional structure of reconstituted discoidal HDL (rdHDL) particles, using a shortened construct of human apolipoprotein A-I, determined from a combination of nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM) data. The rdHDL particles feature a protein double belt surrounding a lipid bilayer patch in an antiparallel fashion. The integrity of this structure is maintained by up to 28 salt bridges and a zipper-like pattern of cation-π interactions between helices 4 and 6. To accommodate a hydrophobic interior, a gross 'right-to-right' rotation of the helices after lipidation is necessary. The structure reflects the complexity required for a shuttling container to hold a fluid lipid or cholesterol interior at a protein:lipid ratio of 1:50.
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| 13. |
- Brown, Alan, et al.
(författare)
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Structures of the human mitochondrial ribosome in native states of assembly
- 2017
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 24:10, s. 866-869
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Tidskriftsartikel (refereegranskat)abstract
- Mammalian mitochondrial ribosomes (mitoribosomes) have less rRNA content and 36 additional proteins compared with the evolutionarily related bacterial ribosome. These differences make the assembly of mitoribosomes more complex than the assembly of bacterial ribosomes, but the molecular details of mitoribosomal biogenesis remain elusive. Here, we report the structures of two late-stage assembly intermediates of the human mitoribosomal large subunit (mt-LSU) isolated from a native pool within a human cell line and solved by cryo-EM to similar to 3-angstrom resolution. Comparison of the structures reveals insights into the timing of rRNA folding and protein incorporation during the final steps of ribosomal maturation and the evolutionary adaptations that are required to preserve biogenesis after the structural diversification of mitoribosomes. Furthermore, the structures redefine the ribosome silencing factor (RsfS) family as multifunctional biogenesis factors and identify two new assembly factors (L0R8F8 and mt-ACP) not previously implicated in mitoribosomal biogenesis.
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| 14. |
- Burke, David F., et al.
(författare)
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Towards a structurally resolved human protein interaction network
- 2023
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 30:2, s. 216-225
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Tidskriftsartikel (refereegranskat)abstract
- Cellular functions are governed by molecular machines that assemble through protein-protein interactions. Their atomic details are critical to studying their molecular mechanisms. However, fewer than 5% of hundreds of thousands of human protein interactions have been structurally characterized. Here we test the potential and limitations of recent progress in deep-learning methods using AlphaFold2 to predict structures for 65,484 human protein interactions. We show that experiments can orthogonally confirm higher-confidence models. We identify 3,137 high-confidence models, of which 1,371 have no homology to a known structure. We identify interface residues harboring disease mutations, suggesting potential mechanisms for pathogenic variants. Groups of interface phosphorylation sites show patterns of co-regulation across conditions, suggestive of coordinated tuning of multiple protein interactions as signaling responses. Finally, we provide examples of how the predicted binary complexes can be used to build larger assemblies helping to expand our understanding of human cell biology.
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| 15. |
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| 16. |
- Choi, Junhong, et al.
(författare)
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2'-O-methylation in mRNA disrupts tRNA decoding during translation elongation
- 2018
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Nature. - 1545-9993 .- 1545-9985. ; 25:3, s. 208-216
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Tidskriftsartikel (refereegranskat)abstract
- Chemical modifications of mRNA may regulate many aspects of mRNA processing and protein synthesis. Recently, 2 '-O-methylation of nucleotides was identified as a frequent modification in translated regions of human mRNA, showing enrichment in codons for certain amino acids. Here, using single-molecule, bulk kinetics and structural methods, we show that 2 '-O-methylation within coding regions of mRNA disrupts key steps in codon reading during cognate tRNA selection. Our results suggest that 2 '-O-methylation sterically perturbs interactions of ribosomal-monitoring bases (G530, A1492 and A1493) with cognate codon-anticodon helices, thereby inhibiting downstream GTP hydrolysis by elongation factor Tu (EF-Tu) and A-site tRNA accommodation, leading to excessive rejection of cognate aminoacylated tRNAs in initial selection and proofreading. Our current and prior findings highlight how chemical modifications of mRNA tune the dynamics of protein synthesis at different steps of translation elongation.
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| 17. |
- Choi, Junhong, et al.
(författare)
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N-6-methyladenosine in mRNA disrupts tRNA selection and translation-elongation dynamics
- 2016
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 23:2, s. 110-
-
Tidskriftsartikel (refereegranskat)abstract
- N-6-methylation of adenosine (forming m(6)A) is the most abundant post-transcriptional modification within the coding region of mRNA, but its role during translation remains unknown. Here, we used bulk kinetic and single-molecule methods to probe the effect of m(6)A in mRNA decoding. Although m(6)A base-pairs with uridine during decoding, as shown by X-ray crystallographic analyses of Thermus thermophilus ribosomal complexes, our measurements in an Escherichia coli translation system revealed that m(6)A modification of mRNA acts as a barrier to tRNA accommodation and translation elongation. The interaction between an m(6)A-modified codon and cognate tRNA echoes the interaction between a near-cognate codon and tRNA, because delay in tRNA accommodation depends on the position and context of m(6)A within codons and on the accuracy level of translation. Overall, our results demonstrate that chemical modification of mRNA can change translational dynamics.
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| 18. |
- Cohen, Samuel I A, et al.
(författare)
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A molecular chaperone breaks the catalytic cycle that generates toxic Aβ oligomers.
- 2015
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 22:3, s. 207-213
-
Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease is an increasingly prevalent neurodegenerative disorder whose pathogenesis has been associated with aggregation of the amyloid-β peptide (Aβ42). Recent studies have revealed that once Aβ42 fibrils are generated, their surfaces effectively catalyze the formation of neurotoxic oligomers. Here we show that a molecular chaperone, a human Brichos domain, can specifically inhibit this catalytic cycle and limit human Aβ42 toxicity. We demonstrate in vitro that Brichos achieves this inhibition by binding to the surfaces of fibrils, thereby redirecting the aggregation reaction to a pathway that involves minimal formation of toxic oligomeric intermediates. We verify that this mechanism occurs in living mouse brain tissue by cytotoxicity and electrophysiology experiments. These results reveal that molecular chaperones can help maintain protein homeostasis by selectively suppressing critical microscopic steps within the complex reaction pathways responsible for the toxic effects of protein misfolding and aggregation.
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| 19. |
- Coincon, Mathieu, et al.
(författare)
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Crystal structures reveal the molecular basis of ion translocation in sodium/proton antiporters
- 2016
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 23:3, s. 248-255
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Tidskriftsartikel (refereegranskat)abstract
- To fully understand the transport mechanism of Na+/H+ exchangers, it is necessary to clearly establish the global rearrangements required to facilitate ion translocation. Currently, two different transport models have been proposed. Some reports have suggested that structural isomerization is achieved through large elevator-like rearrangements similar to those seen in the structurally unrelated sodium-coupled glutamate-transporter homolog Glt(ph). Others have proposed that only small domain movements are required for ion exchange, and a conventional rocking-bundle model has been proposed instead. Here, to resolve these differences, we report atomic-resolution structures of the same Na+/H+ antiporter (NapA from Thermus thermophilus) in both outward- and inward-facing conformations. These data combined with cross-linking, molecular dynamics simulations and isothermal calorimetry suggest that Na+/H+ antiporters provide alternating access to the ion-binding site by using elevator-like structural transitions.
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| 20. |
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| 21. |
- Doerig, Christian, et al.
(författare)
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A parasite calcium switch and Achilles' heel revealed
- 2010
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 17:5, s. 541-543
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Tidskriftsartikel (refereegranskat)
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| 22. |
- Doksani, Ylli, et al.
(författare)
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The risky business of ADP-ribosylating telomeric DNA
- 2024
-
Ingår i: Nature Structural & Molecular Biology. - : NATURE PORTFOLIO. - 1545-9993 .- 1545-9985.
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Tidskriftsartikel (refereegranskat)abstract
- ADP-ribosylation regulates the activity of numerous proteins involved in the DNA damage response and repair. A new study shows that telomeric DNA can be ADP-ribosylated by PARP1, and prompt removal of the ADP-ribose by TARG1 is essential to preserve telomere integrity, unveiling DNA-ADP-ribosylation as a novel player in telomere stability.
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| 23. |
- Egelhofer, Thea A, et al.
(författare)
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An assessment of histone-modification antibody quality
- 2011
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 18:1, s. 91-93
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Tidskriftsartikel (refereegranskat)abstract
- We have tested the specificity and utility of more than 200 antibodies raised against 57 different histone modifications in Drosophila melanogaster, Caenorhabditis elegans and human cells. Although most antibodies performed well, more than 25% failed specificity tests by dot blot or western blot. Among specific antibodies, more than 20% failed in chromatin immunoprecipitation experiments. We advise rigorous testing of histone-modification antibodies before use, and we provide a website for posting new test results (http://compbio.med.harvard.edu/antibodies/).
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| 24. |
- Ekwall, Karl
(författare)
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'Arc' escorts siRNAs in heterochromatin assembly
- 2007
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 14:3, s. 178-179
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- RNA interference (RNAi) is important in directing heterochromatin assembly at centromeres in fission yeast, which is crucial for maintaining a stable genome through mitotic and meiotic divisions. In this issue, Buker et al. describe a new Argonaute siRNA chaperone (ARC) that converts duplex RNA to single-stranded RNA. This is a previously unknown step in the RNAi-directed heterochromatin-formation pathway.
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| 25. |
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| 26. |
- Fernandez-Marino, Ana I., et al.
(författare)
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Gating interaction maps reveal a noncanonical electromechanical coupling mode in the Shaker K+ channel
- 2018
-
Ingår i: Nature Structural & Molecular Biology. - : Nature Publishing Group. - 1545-9993 .- 1545-9985. ; 25:4, s. 320-326
-
Tidskriftsartikel (refereegranskat)abstract
- Membrane potential regulates the activity of voltage-dependent ion channels via specialized voltage-sensing modules, but the mechanisms involved in coupling voltage-sensor movement to pore opening remain unclear owing to a lack of resting state structures and robust methods to identify allosteric pathways. Here, using a newly developed interaction-energy analysis, we probe the interfaces of the voltage-sensing and pore modules in the Drosophila Shaker K+ channel. Our measurements reveal unexpectedly strong equilibrium gating interactions between contacts at the S4 and S5 helices in addition to those between S6 and the S4-S5 linker. Network analysis of MD trajectories shows that the voltage-sensor and pore motions are linked by two distinct pathways: a canonical pathway through the S4-S5 linker and a hitherto unknown pathway akin to rack-and-pinion coupling involving the S4 and S5 helices. Our findings highlight the central role of the S5 helix in electromechanical transduction in the voltage-gated ion channel (VGIC) superfamily.
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| 27. |
- Flagmeier, Patrick, et al.
(författare)
-
Direct measurement of lipid membrane disruption connects kinetics and toxicity of Aβ42 aggregation
- 2020
-
Ingår i: Nature Structural and Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 27:10, s. 886-891
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of amyloid deposits in human tissues is a defining feature of more than 50 medical disorders, including Alzheimer’s disease. Strong genetic and histological evidence links these conditions to the process of protein aggregation, yet it has remained challenging to identify a definitive connection between aggregation and pathogenicity. Using time-resolved fluorescence microscopy of individual synthetic vesicles, we show for the Aβ42 peptide implicated in Alzheimer’s disease that the disruption of lipid bilayers correlates linearly with the time course of the levels of transient oligomers generated through secondary nucleation. These findings indicate a specific role of oligomers generated through the catalytic action of fibrillar species during the protein aggregation process in driving deleterious biological function and establish a direct causative connection between amyloid formation and its pathological effects.
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| 28. |
- Fong, Nova, et al.
(författare)
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Fast ribozyme cleavage releases transcripts from RNA polymerase II and aborts co-transcriptional pre-mRNA processing
- 2009
-
Ingår i: Nature Structural & Molecular Biology. - : Nature America Inc. - 1545-9993 .- 1545-9985. ; 16:9, s. 916-923
-
Tidskriftsartikel (refereegranskat)abstract
- Adenosine-to-inosine (A-to-I) editing has been shown to be an important mechanism that increases protein diversity in the brain of organisms from human to fly. The family of ADAR enzymes converts some adenosines of RNA duplexes to inosines through hydrolytic deamination. The adenosine recognition mechanism is still largely unknown. Here, to investigate it, we analyzed a set of selectively edited substrates with a cluster of edited sites. We used a large set of individual transcripts sequenced by the 454 sequencing technique. On average, we analyzed 570 single transcripts per edited region at four different developmental stages from embryogenesis to adulthood. To our knowledge, this is the first time, large-scale sequencing has been used to determine synchronous editing events. We demonstrate that edited sites are only coupled within specific distances from each other. Furthermore, our results show that the coupled sites of editing are positioned on the same side of a helix, indicating that the three-dimensional structure is key in ADAR enzyme substrate recognition. Finally, we propose that editing by the ADAR enzymes is initiated by their attraction to one principal site in the substrate.
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| 29. |
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| 30. |
- Gianni, Stefano, et al.
(författare)
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Structural characterization of a misfolded intermediate populated during the folding process of a PDZ domain
- 2010
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 17:12, s. 1431-1437
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Tidskriftsartikel (refereegranskat)abstract
- Incorrectly folded states transiently populated during the protein folding process are potentially prone to aggregation and have been implicated in a range of misfolding disorders that include Alzheimer's and Parkinson's diseases. Despite their importance, however, the structures of these states and the mechanism of their formation have largely escaped detailed characterization because of their short-lived nature. Here we present the structures of all the major states involved in the folding process of a PDZ domain, which include an off-pathway misfolded intermediate. By using a combination of kinetic, protein engineering, biophysical and computational techniques, we show that the misfolded intermediate is characterized by an alternative packing of the N-terminal β-hairpin onto an otherwise native-like scaffold. Our results suggest a mechanism of formation of incorrectly folded transient compact states by which misfolded structural elements are assembled together with more extended native-like regions.
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| 31. |
- Gowda, Naveen K. C., et al.
(författare)
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Nucleotide exchange factors Fes1 and HspBP1 mimic substrate to release misfolded proteins from Hsp70
- 2018
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 25:1, s. 83-
-
Tidskriftsartikel (refereegranskat)abstract
- Protein quality control depends on the tight regulation of interactions between molecular chaperones and polypeptide substrates. Substrate release from the chaperone Hsp70 is triggered by nucleotide-exchange factors (NEFs) that control folding and degradation fates via poorly understood mechanisms. We found that the armadillo-type NEFs budding yeast Fes1 and its human homolog HspBP1 employ flexible N-terminal release domains (RDs) with substrate-mimicking properties to ensure the efficient release of persistent substrates from Hsp70. The RD contacts the substrate-binding domain of the chaperone, competes with peptide substrate for binding and is essential for proper function in yeast and mammalian cells. Thus, the armadillo domain engages Hsp70 to trigger nucleotide exchange, whereas the RD safeguards the release of substrates. Our findings provide fundamental mechanistic insight into the functional specialization of Hsp70 NEFs and have implications for the understanding of proteostasis-related disorders, including Marinesco-Sjögren syndrome.
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| 32. |
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| 33. |
- Hainzl, Tobias, et al.
(författare)
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Structural basis of signal-sequence recognition by the signal recognition particle
- 2011
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 18:3, s. 389-391
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Tidskriftsartikel (refereegranskat)abstract
- The signal recognition particle (SRP) recognizes and binds the signal sequence of nascent proteins as they emerge from the ribosome. We present here the 3.0-Å structure of a signal sequence bound to the Methanococcus jannaschii SRP core. Structural comparison with the free SRP core shows that signal-sequence binding induces formation of the GM-linker helix and a 180° flip of the NG domain—structural changes that ensure a hierarchical succession of events during protein targeting.
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| 34. |
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| 35. |
- Helleday, T
(författare)
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PrimPol breaks replication barriers
- 2013
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Ingår i: Nature structural & molecular biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 20:12, s. 1348-1350
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 36. |
- Hernandez-Valladares, Maria, et al.
(författare)
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Structural characterization of a capping protein interaction motif defines a family of actin filament regulators.
- 2010
-
Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 17:4, s. 497-503
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Tidskriftsartikel (refereegranskat)abstract
- Capping protein (CP) regulates actin dynamics by binding the barbed ends of actin filaments. Removal of CP may be one means to harness actin polymerization for processes such as cell movement and endocytosis. Here we structurally and biochemically investigated a CP interaction (CPI) motif present in the otherwise unrelated proteins CARMIL and CD2AP. The CPI motif wraps around the stalk of the mushroom-shaped CP at a site distant from the actin-binding interface, which lies on the top of the mushroom cap. We propose that the CPI motif may act as an allosteric modulator, restricting CP to a low-affinity, filament-binding conformation. Structure-based sequence alignments extend the CPI motif-containing family to include CIN85, CKIP-1, CapZIP and a relatively uncharacterized protein, WASHCAP (FAM21). Peptides comprising these CPI motifs are able to inhibit CP and to uncap CP-bound actin filaments.
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| 37. |
- Hogg, Matthew, et al.
(författare)
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Structural basis for processive DNA synthesis by yeast DNA polymerase ε
- 2014
-
Ingår i: Nature Structural & Molecular Biology. - : Nature Publishing Group. - 1545-9993 .- 1545-9985. ; 21:1, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- DNA polymerase ε (Pol ε) is a high-fidelity polymerase that has been shown to participate in leading-strand synthesis during DNA replication in eukaryotic cells. We present here a ternary structure of the catalytic core of Pol ε (142 kDa) from Saccharomyces cerevisiae in complex with DNA and an incoming nucleotide. This structure provides information about the selection of the correct nucleotide and the positions of amino acids that might be critical for proofreading activity. Pol ε has the highest fidelity among B-family polymerases despite the absence of an extended b-hairpin loop that is required for high-fidelity replication by other B-family polymerases. Moreover, the catalytic core has a new domain that allows Pol ε to encircle the nascent doublestranded DNA. Altogether, the structure provides an explanation for the high processivity and high fidelity of leading-strand DNA synthesis in eukaryotes
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| 38. |
- Ismail, Nurzian, et al.
(författare)
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A biphasic pulling force acts on transmembrane helices during translocon mediated membrane integration
- 2012
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 19:10, s. 1018-1022
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Tidskriftsartikel (refereegranskat)abstract
- Membrane proteins destined for insertion into the inner membrane of bacteria or the endoplasmic reticulum membrane in eukaryotic cells are synthesized by ribosomes bound to the bacterial SecYEG or the homologous eukaryotic Sec61 translocon. During co-translational membrane integration, transmembrane alpha-helical segments in the nascent chain exit the translocon through a lateral gate that opens toward the surrounding membrane, but the mechanism of lateral exit is not well understood. In particular, little is known about how a transmembrane helix behaves when entering and exiting the translocon. Using translation-arrest peptides from bacterial SecM proteins and from the mammalian Xbp1 protein as force sensors, we show that substantial force is exerted on a transmembrane helix at two distinct points during its transit through the translocon channel, providing direct insight into the dynamics of membrane integration.
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| 39. |
- Ismail, Nurzian, et al.
(författare)
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Charge-driven dynamics of nascent-chain movement through the SecYEG translocon
- 2015
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 22:2, s. 145-149
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Tidskriftsartikel (refereegranskat)abstract
- On average, every fifth residue in secretory proteins carries either a positive or a negative charge. In a bacterium such as Escherichia coli, charged residues are exposed to an electric field as they transit through the inner membrane, and this should generate a fluctuating electric force on a translocating nascent chain. Here, we have used translational arrest peptides as in vivo force sensors to measure this electric force during cotranslational chain translocation through the SecYEG translocon. We find that charged residues experience a biphasic electric force as they move across the membrane, including an early component with a maximum when they are 47-49 residues away from the ribosomal P site, followed by a more slowly varying component. The early component is generated by the transmembrane electric potential, whereas the second may reflect interactions between charged residues and the periplasmic membrane surface.
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| 40. |
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| 41. |
- Jore, Matthijs, et al.
(författare)
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Structural basis for CRISPR RNA-guided DNA recognition by Cascade
- 2011
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 18:5, s. 529-536
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Tidskriftsartikel (refereegranskat)abstract
- The CRISPR (clustered regularly interspaced short palindromic repeats) immune system in prokaryotes uses small guide RNAs to neutralize invading viruses and plasmids. In Escherichia coli, immunity depends on a ribonucleoprotein complex called Cascade. Here we present the composition and low-resolution structure of Cascade and show how it recognizes double-stranded DNA (dsDNA) targets in a sequence-specific manner. Cascade is a 405-kDa complex comprising five functionally essential CRISPR-associated (Cas) proteins (CasA1B2C6D1E1) and a 61-nucleotide CRISPR RNA (crRNA) with 5′-hydroxyl and 2′,3′-cyclic phosphate termini. The crRNA guides Cascade to dsDNA target sequences by forming base pairs with the complementary DNA strand while displacing the noncomplementary strand to form an R-loop. Cascade recognizes target DNA without consuming ATP, which suggests that continuous invader DNA surveillance takes place without energy investment. The structure of Cascade shows an unusual seahorse shape that undergoes conformational changes when it binds target DNA.
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| 42. |
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| 43. |
- Kelly, John J., et al.
(författare)
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Snapshots of actin and tubulin folding inside the TRiC chaperonin
- 2022
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Ingår i: Nature Structural and Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 29:5, s. 420-429
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Tidskriftsartikel (refereegranskat)abstract
- The integrity of a cell’s proteome depends on correct folding of polypeptides by chaperonins. The chaperonin TCP-1 ring complex (TRiC) acts as obligate folder for >10% of cytosolic proteins, including he cytoskeletal proteins actin and tubulin. Although its architecture and how it recognizes folding substrates are emerging from structural studies, the subsequent fate of substrates inside the TRiC chamber is not defined. We trapped endogenous human TRiC with substrates (actin, tubulin) and cochaperone (PhLP2A) at different folding stages, for structure determination by cryo-EM. The already-folded regions of client proteins are anchored at the chamber wall, positioning unstructured regions toward the central space to achieve their native fold. Substrates engage with different sections of the chamber during the folding cycle, coupled to TRiC open-and-close transitions. Further, the cochaperone PhLP2A modulates folding, acting as a molecular strut between substrate and TRiC chamber. Our structural snapshots piece together an emerging model of client protein folding within TRiC.
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| 44. |
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| 45. |
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| 46. |
- Larsson, Gunilla, et al.
(författare)
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Crystal structure of the Escherichia coli dUTPase in complex with a substrate analogue (dUDP)
- 1996
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 3:6, s. 532-538
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Tidskriftsartikel (refereegranskat)abstract
- We have determined the structure of the homotrimeric dUTPase from Escherichia coli, complexed with an inhibitor and substrate analogue, dUDP. Three molecules of dUDP are found symmetrically bound per trimer, each in a shallow cleft between adjacent subunits, interacting with evolutionary conserved residues. The interactions of the uracil ring and the deoxypentose with the protein are consistent with the high specificity of the enzyme with respect to these groups. The positions of the two phosphate groups and adjacent water molecules are discussed in relation to the mechanism and kinetics of catalysis. The role that dUTPase plays in DNA metabolism makes the enzyme a potential target for chemotherapeutic drugs: the results presented here will aid in the design and development of inhibitory compounds.
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| 47. |
- Larsson, Karl-Magnus, et al.
(författare)
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Structural mechanism of allosteric substrate specificity regulation in a ribonucleotide reductase
- 2004
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 11:11, s. 1142-1149
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Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides into deoxyribonucleotides, which constitute the precursor pools used for DNA synthesis and repair. Imbalances in these pools increase mutational rates and are detrimental to the cell. Balanced precursor pools are maintained primarily through the regulation of the RNR substrate specificity. Here, the molecular mechanism of the allosteric substrate specificity regulation is revealed through the structures of a dimeric coenzyme B12-dependent RNR from Thermotoga maritima, both in complexes with four effector-substrate nucleotide pairs and in three complexes with only effector. The mechanism is based on the flexibility of loop 2, a key structural element, which forms a bridge between the specificity effector and substrate nucleotides. Substrate specificity is achieved as different effectors and their cognate substrates stabilize specific discrete loop 2 conformations. The mechanism of substrate specificity regulation is probably general for most class I and class II RNRs.
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| 48. |
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| 49. |
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| 50. |
- Liljas, Anders
(författare)
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Zooming in on eukaryotic translation initiation.
- 2013
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 20:10, s. 1141-1142
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Tidskriftsartikel (refereegranskat)
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