Change search
Refine search result
1 - 14 of 14
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    da Silva, Diogo V.
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nordholm, Johan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Dou, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wang, Hao
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Rossman, Jeremy S.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    The Influenza Virus Neuraminidase Protein Transmembrane and Head Domains Have Coevolved2015In: Journal of Virology, ISSN 0022-538X, E-ISSN 1098-5514, Vol. 89, no 2, p. 1094-1104Article in journal (Refereed)
    Abstract [en]

    Transmembrane domains (TMDs) from single-spanning membrane proteins are commonly viewed as membrane anchors for functional domains. Influenza virus neuraminidase (NA) exemplifies this concept, as it retains enzymatic function upon proteolytic release from the membrane. However, the subtype 1 NA TMDs have become increasingly more polar in human strains since 1918, which suggests that selection pressure exists on this domain. Here, we investigated the N1 TMD-head domain relationship by exchanging a prototypical old TMD (1933) with a recent (2009), more polar TMD and an engineered hydrophobic TMD. Each exchange altered the TMD association, decreased the NA folding efficiency, and significantly reduced viral budding and replication at 37 degrees C compared to at 33 degrees C, at which NA folds more efficiently. Passaging the chimera viruses at 37 degrees C restored the NA folding efficiency, viral budding, and infectivity by selecting for NA TMD mutations that correspond with their polar or hydrophobic assembly properties. These results demonstrate that single-spanning membrane protein TMDs can influence distal domain folding, as well as membrane-related processes, and suggest the NA TMD in H1N1 viruses has become more polar to maintain compatibility with the evolving enzymatic head domain. IMPORTANCE The neuranainidase (NA) protein from influenza A viruses (IAVs) functions to promote viral release and is one of the major surface antigens. The receptor-destroying activity in NA resides in the distal head domain that is linked to the viral membrane by an N-terminal hydrophobic transmembrane domain (TMD). Over the last century, the subtype 1 NA TMDs (N1) in human H1N1 viruses have become increasingly more polar, and the head domains have changed to alter their antigenicity. Here, we provide the first evidence that an old N1 head domain from 1933 is incompatible with a recent (2009), more polar N1 TMD sequence and that, during viral replication, the head domain drives the selection of TMD mutations. These mutations modify the intrinsic TMD assembly to restore the head domain folding compatibility and the resultant budding deficiency. This likely explains why the N1 TMDs have become more polar and suggests the N1 TMD and head domain have coevolved.

  • 2.
    da Silva, Diogo V.
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nordholm, Johan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Madjo, Ursula
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pfeiffer, Annika
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Assembly of Subtype 1 Influenza Neuraminidase Is Driven by Both the Transmembrane and Head Domains2013In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 288, no 1, p. 644-653Article in journal (Refereed)
    Abstract [en]

    Neuraminidase (NA) is one of the two major influenza surface antigens and the main influenza drug target. Although NA has been well characterized and thought to function as a tetramer, the role of the transmembrane domain (TMD) in promoting proper NA assembly has not been systematically studied. Here, we demonstrate that in the absence of the TMD, NA is synthesized and transported in a predominantly inactive state. Substantial activity was rescued by progressive truncations of the stalk domain, suggesting the TMD contributes to NA maturation by tethering the stalk to the membrane. To analyze how the TMD supports NA assembly, the TMD was examined by itself. The NA TMD formed a homotetramer and efficiently trafficked to the plasma membrane, indicating the TMD and enzymatic head domain drive assembly together through matching oligomeric states. In support of this, an unrelated strong oligomeric TMD rescued almost full NA activity, whereas the weak oligomeric mutant of this TMD restored only half of wild type activity. These data illustrate that a large soluble domain can force assembly with a poorly compatible TMD; however, optimal assembly requires coordinated oligomerization between the TMD and the soluble domain.

  • 3. Dai, Meiling
    et al.
    Guo, Hongbo
    Dortmans, Jos C. F. M.
    Dekkers, Jojanneke
    Nordholm, Johan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    van Kuppeveld, Frank J. M.
    de Vries, Erik
    de Haan, Cornelis A. M.
    Identification of Residues That Affect Oligomerization and/or Enzymatic Activity of Influenza Virus H5N1 Neuraminidase Proteins2016In: Journal of Virology, ISSN 0022-538X, E-ISSN 1098-5514, Vol. 90, no 20, p. 9457-9470Article in journal (Refereed)
    Abstract [en]

    Influenza A virus (IAV) attachment to and release from sialoside receptors is determined by the balance between hemagglutinin (HA) and neuraminidase (NA). The molecular determinants that mediate the specificity and activity of NA are still poorly understood. In this study, we aimed to design the optimal recombinant soluble NA protein to identify residues that affect NA enzymatic activity. To this end, recombinant soluble versions of four different NA proteins from H5N1 viruses were compared with their full-length counterparts. The soluble NA ectodomains were fused to three commonly used tetramerization domains. Our results indicate that the particular oligomerization domain used does not affect the K-m value but may affect the specific enzymatic activity. This particularly holds true when the stalk domain is included and for NA ectodomains that display a low intrinsic ability to oligomerize. NA ectodomains extended with a Tetrabrachion domain, which forms a nearly parallel four-helix bundle, better mimicked the enzymatic properties of full-length proteins than when other coiled-coil tetramerization domains were used, which probably distort the stalk domain. Comparison of different NA proteins and mutagenic analysis of recombinant soluble versions thereof resulted in the identification of several residues that affected oligomerization of the NA head domain (position 95) and therefore the specific activity or sialic acid binding affinity (K-m value; positions 252 and 347). This study demonstrates the potential of using recombinant soluble NA proteins to reveal determinants of NA assembly and enzymatic activity. IMPORTANCE The IAV HA and NA glycoproteins are important determinants of host tropism and pathogenicity. However, NA is relatively understudied compared to HA. Analysis of soluble versions of these glycoproteins is an attractive way to study their activities, as they are easily purified from cell culture media and applied in downstream assays. In the present study, we analyzed the enzymatic activity of different NA ectodomains with three commonly used tetramerization domains and compared them with fulllength NA proteins. By performing a mutagenic analysis, we identified several residues that affected NA assembly, activity, and/or substrate binding. In addition, our results indicate that the design of the recombinant soluble NA protein, including the particular tetramerization domain, is an important determinant for maintaining the enzymatic properties within the head domain. NA ectodomains extended with a Tetrabrachion domain better mimicked the full-length proteins than when the other tetramerization domains were used.

  • 4.
    Dou, Dan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    da Silva, Diogo V.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nordholm, Johan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wang, Hao
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Type II transmembrane domain hydrophobicity dictates the cotranslational dependence for inversion2014In: Molecular Biology of the Cell, ISSN 1059-1524, E-ISSN 1939-4586, Vol. 25, no 21, p. 3363-3374Article in journal (Refereed)
    Abstract [en]

    Membrane insertion by the Sec61 translocon in the endoplasmic reticulum (ER) is highly dependent on hydrophobicity. This places stringent hydrophobicity requirements on transmembrane domains (TMDs) from single-spanning membrane proteins. On examining the single-spanning influenza A membrane proteins, we found that the strict hydrophobicity requirement applies to the N-out-C-in HA and M2 TMDs but not the N-in-C-out TMDs from the type II membrane protein neuraminidase (NA). To investigate this discrepancy, we analyzed NA TMDs of varying hydrophobicity, followed by increasing polypeptide lengths, in mammalian cells and ER microsomes. Our results show that the marginally hydrophobic NA TMDs (Delta G(app) > 0 kcal/mol) require the cotranslational insertion process for facilitating their inversion during translocation and a positively charged N-terminal flanking residue and that NA inversion enhances its plasma membrane localization. Overall the cotranslational inversion of marginally hydrophobic NA TMDs initiates once similar to 70 amino acids past the TMD are synthesized, and the efficiency reaches 50% by similar to 100 amino acids, consistent with the positioning of this TMD class in type II human membrane proteins. Inversion of the M2 TMD, achieved by elongating its C-terminus, underscores the contribution of cotranslational synthesis to TMD inversion.

  • 5.
    Dou, Dan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hernández-Neuta, Iván
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Wang, Hao
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Östbye, Henrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Qian, Xiaoyan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Thiele, Swantje
    Resa-Infante, Patricia
    Mounogou Kouassi, Nancy
    Sender, Vicky
    Hentrich, Karina
    Mellroth, Peter
    Henriques-Normark, Birgitta
    Gabriel, Gülsah
    Nilsson, Mats
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Analysis of IAV Replication and Co-infection Dynamics by a Versatile RNA Viral Genome Labeling Method2017In: Cell reports, ISSN 2211-1247, E-ISSN 2211-1247, Vol. 20, no 1, p. 251-263Article in journal (Refereed)
    Abstract [en]

    Genome delivery to the proper cellular compartment for transcription and replication is a primary goal of viruses. However, methods for analyzing viral genome localization and differentiating genomes with high identity are lacking, making it difficult to investigate entry-related processes and co-examine heterogeneous RNA viral populations. Here, we present an RNA labeling approach for single-cell analysis of RNA viral replication and co-infection dynamics in situ, which uses the versatility of padlock probes. We applied this method to identify influenza A virus (IAV) infections in cells and lung tissue with single-nucleotide specificity and to classify entry and replication stages by gene segment localization. Extending the classification strategy to co-infections of IAVs with single-nucleotide variations, we found that the dependence on intracellular trafficking places a time restriction on secondary co-infections necessary for genome reassortment. Altogether, these data demonstrate how RNA viral genome labeling can help dissect entry and co-infections.

  • 6.
    Dou, Dan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Revol, Rebecca
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Östbye, Henrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wang, Hao
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Influenza A Virus Cell Entry, Replication, Virion Assembly and Movement2018In: Frontiers in Immunology, ISSN 1664-3224, E-ISSN 1664-3224, Vol. 9, article id 1581Article, review/survey (Refereed)
    Abstract [en]

    Influenza viruses replicate within the nucleus of the host cell. This uncommon RNA virus trait provides influenza with the advantage of access to the nuclear machinery during replication. However, it also increases the complexity of the intracellular trafficking that is required for the viral components to establish a productive infection. The segmentation of the influenza genome makes these additional trafficking requirements especially challenging, as each viral RNA (vRNA) gene segment must navigate the network of cellular membrane barriers during the processes of entry and assembly. To accomplish this goal, influenza A viruses (IAVs) utilize a combination of viral and cellular mechanisms to coordinate the transport of their proteins and the eight vRNA gene segments in and out of the cell. The aim of this review is to present the current mechanistic understanding for how IAVs facilitate cell entry, replication, virion assembly, and intercellular movement, in an effort to highlight some of the unanswered questions regarding the coordination of the IAV infection process.

  • 7.
    Karyolaimos, Alexandros
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ampah-Korsah, Henry
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hillenaar, Tamara
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Borras, Anna Mestre
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Dolata, Katarzyna Magdalena
    Sievers, Susanne
    Riedel, Katharina
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Enhancing Recombinant Protein Yields in the E. coli Periplasm by Combining Signal Peptide and Production Rate Screening2019In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 10, article id 1511Article in journal (Refereed)
    Abstract [en]

    Proteins that contain disulfide bonds mainly mature in the oxidative environment of the eukaryotic endoplasmic reticulum or the periplasm of Gram-negative bacteria. In E. coli, disulfide bond containing recombinant proteins are often targeted to the periplasm by an N -terminal signal peptide that is removed once it passes through the Sectranslocon in the cytoplasmic membrane. Despite their conserved targeting function, signal peptides can impact recombinant protein production yields in the periplasm, as can the production rate. Here, we present a combined screen involving different signal peptides and varying production rates that enabled the identification of more optimal conditions for periplasmic production of recombinant proteins with disulfide bonds. The data was generated from two targets, a single chain antibody fragment (BL1) and human growth hormone (hGH), with four different signal peptides and a titratable rhamnose promoter-based system that enables the tuning of protein production rates. Across the screen conditions, the yields for both targets significantly varied, and the optimal signal peptide and rhamnose concentration differed for each protein. Under the optimal conditions, the periplasmic BL1 and hGH were properly folded and active. Our study underpins the importance of combinatorial screening approaches for addressing the requirements associated with the production of a recombinant protein in the periplasm.

  • 8. Mellroth, Peter
    et al.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Eberhardt, Alice
    Ronnlund, Daniel
    Blom, Hans
    Widengren, Jerker
    Normark, Staffan
    Henriques-Normark, Birgitta
    LytA, Major Autolysin of Streptococcus pneumoniae, Requires Access to Nascent Peptidoglycan2012In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 287, no 14, p. 11018-11029Article in journal (Refereed)
    Abstract [en]

    Background: The regulation of cell wall hydrolysis by the pneumococcal autolysin LytA is poorly understood. Results: The cell wall is susceptible to extracellular LytA only during the stationary phase or after cell wall synthesis inhibition. Conclusion: LytA is regulated on the substrate level, where peptidoglycan modifications likely prevent LytA hydrolysis. Significance: The control of amidases is essential for bacterial survival, cell-wall synthesis, and division.

  • 9. Moreno-Pescador, Guillermo
    et al.
    Florentsen, Christoffer D.
    Østbye, Henrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sønder, Stine L.
    Boye, Theresa L.
    Veje, Emilie L.
    Sonne, Alexander K.
    Semsey, Szabolcs
    Nylandsted, Jesper
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bendix, Poul Martin
    Curvature- and Phase-Induced Protein Sorting Quantified in Transfected Cell-Derived Giant Vesicles2019In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 13, no 6, p. 6689-6701Article in journal (Refereed)
    Abstract [en]

    Eukaryotic cells possess a dynamic network of membranes that vary in lipid composition. To perform numerous biological functions, cells modulate their shape and the lateral organization of proteins associated with membranes. The modulation is generally facilitated by physical cues that recruit proteins to specific regions of the membrane. Analyzing these cues is difficult due to the complexity of the membrane conformations that exist in cells. Here, we examine how different types of membrane proteins respond to changes in curvature and to lipid phases found in the plasma membrane. By using giant plasma membrane vesicles derived from transfected cells, the proteins were positioned in the correct orientation and the analysis was performed in plasma membranes with a biological composition. Nanoscale membrane curvatures were generated by extracting nanotubes from these vesicles with an optical trap. The viral membrane protein neuraminidase was not sensitive to curvature, but it did exhibit strong partitioning (coefficient of K = 0.16) disordered membrane regions. In contrast, the membrane repair protein annexin 5 showed a preference for nanotubes with a density up to 10-15 times higher than that on the more flat vesicle membrane. The investigation of nanoscale effects in isolated plasma membranes provides a quantitative platform for studying peripheral and integral membrane proteins in their natural environment.

  • 10.
    Nordholm, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    da Silva, Diogo V.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Damjanovic, Justina
    Dou, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Polar Residues and Their Positional Context Dictate the Transmembrane Domain Interactions of Influenza A Neuraminidases2013In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 288, no 15, p. 10652-10660Article in journal (Refereed)
    Abstract [en]

    Interactions that facilitate transmembrane domain (TMD) dimerization have been identified mainly using synthetic TMDs. Here, we investigated how inherent properties within natural TMDs modulate their interaction strength by exploiting the sequence variation in the nine neuraminidase subtypes (N1-N9) and the prior knowledge that a N1 TMD oligomerizes. Initially, consensus TMDs were created from the influenza A virus database, and their interaction strengths were measured in a biological membrane system. The TMD interactions increased with respect to decreasing hydrophobicity across the subtypes (N1-N9) and within the human N1 subtype where the N1 TMDs from the pandemic H1N1 strain of swine origin were found to be significantly less hydrophobic. The hydrophobicity correlation was attributed to the conserved amphipathicity within the TMDs as the interactions were abolished by mutating residues on the polar faces that are unfavorably positioned in the membrane. Similarly, local changes enhanced the interactions only when a larger polar residue existed on the appropriate face in an unfavorable membrane position. Together, the analysis of this unique natural TMD data set demonstrates how polar-mediated TMD interactions from bitopic proteins depend on which polar residues are involved and their positioning with respect to the helix and the membrane bilayer.

  • 11.
    Nordholm, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Petitou, Jeanne
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Östbye, Henrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    da Silva, Diogo V.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Dou, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wang, Hao
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Translational regulation of viral secretory proteins by the 5 ' coding regions and a viral RNA-binding protein2017In: Journal of Cell Biology, ISSN 0021-9525, E-ISSN 1540-8140, Vol. 216, no 8, p. 2283-2293Article in journal (Refereed)
    Abstract [en]

    A primary function of 5' regions in many secretory protein mRNAs is to encode an endoplasmic reticulum (ER) targeting sequence. In this study, we show how the regions coding for the ER-targeting sequences of the influenza glycoproteins NA and HA also function as translational regulatory elements that are controlled by the viral RNA-binding protein (RBP) NS1. The translational increase depends on the nucleotide composition and 5' positioning of the ER-targeting sequence coding regions and is facilitated by the RNA-binding domain of NS1, which can associate with ER membranes. Inserting the ER-targeting sequence coding region of NA into different 5' UTRs confirmed that NS1 can promote the translation of secretory protein mRNAs based on the nucleotides within this region rather than the resulting amino acids. By analyzing human protein mRNA sequences, we found evidence that this mechanism of using 5' coding regions and particular RBPs to achieve gene-specific regulation may extend to human-secreted proteins.

  • 12.
    Schiller, Nina
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Cymer, Florian
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Magoulopoulou, Anastasia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Mutational analysis of the human Xbp1 translational arrest peptide and construction of arrest-enhanced variantsManuscript (preprint) (Other academic)
    Abstract [en]

    Xbp1, a protein involved in the unfolded protein response, is a rare example of a mammalian protein that contains a well-defined translational arrest peptide (AP). In order to define the critical residues in the Xbp1u AP, and to search for variants with stronger arrest potency than the wildtype Xbp1u AP, we have carried out a full mutagenesis scan where each residue in the AP was replaced by the other 19 natural amino acids. We find that 10 of the 21 mutagenized positions are optimal already in the wildtype Xbp1 AP, while certain mutations in the remaining residues lead to a strong increase in the arrest potency. Xbp1 has thus evolved to induce an intermediate level of translational arrest, and versions with much stronger arrest efficiency exist. We further show Xbp1- induced translational arrest is reduced in response to increased tension in the nascent chain, making it possible to carry out studies in mammalian systems of cotranslational processes such as membrane protein assembly and protein folding by using suitable Xbp1 AP variants as “force sensors”, as has been done previously in E. coli using bacterial APs.

  • 13.
    Wang, Hao
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Dou, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Östbye, Henrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Revol, Rebecca
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Structural restrictions for influenza neuraminidase activity promote adaptation and diversification2019In: Nature Microbiology, E-ISSN 2058-5276Article in journal (Refereed)
    Abstract [en]

    Influenza neuraminidase (NA) is a sialidase that contributes to viral mobility by removing the extracellular receptors for the haemagglutinin (HA) glycoprotein. However, it remains unclear why influenza NAs evolved to function as Ca2+-dependent tetramers that display variable stability. Here, we show that the Ca2+ ion located at the centre of the NA tetramer is a major stability determinant, as this Ca2+ ion is required for catalysis and its binding affinity varies between NAs. By examining NAs from 2009 pandemic-like H1N1 viruses, we traced the affinity variation to local substitutions that cause residues in the central Ca2+-binding pocket to reposition. A temporal analysis revealed that these local substitutions predictably alter the stability of the 2009 pandemic-like NAs and contribute to the tendency for the stability to vary up and down over time. In addition to the changes in stability, the structural plasticity of NA was also shown to support the formation of heterotetramers, which creates a mechanism for NA to obtain hybrid properties and propagate suboptimal mutants. Together, these results demonstrate how the structural restrictions for activity provide influenza NA with several mechanisms for adaptation and diversification.

  • 14. Younis, Shady
    et al.
    Kamel, Wael
    Falkeborn, Tina
    Wang, Hao
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Yu, Di
    Daniels, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Essand, Magnus
    Hinkula, Jorma
    Akusjarvi, Goran
    Andersson, Leif
    Multiple nuclear-replicating viruses require the stress-induced protein ZC3H11A for efficient growth2018In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 115, no 16, p. e3808-E3816Article in journal (Refereed)
    Abstract [en]

    The zinc finger CCCH-type containing 11A (ZC3H11A) gene encodes a well-conserved zinc finger protein that may function in mRNA export as it has been shown to associate with the transcription export (TREX) complex in proteomic screens. Here, we report that ZC3H11A is a stress-induced nuclear protein with RNA-binding capacity that localizes to nuclear splicing speckles. During an adenovirus infection, the ZC3H11A protein and splicing factor SRSF2 relocalize to nuclear regions where viral DNA replication and transcription take place. Knockout (KO) of ZC3H11A in HeLa cells demonstrated that several nuclear-replicating viruses are dependent on ZC3H11A for efficient growth (HIV, influenza virus, herpes simplex virus, and adenovirus), whereas cytoplasmic replicating viruses are not (vaccinia virus and Semliki Forest virus). High-throughput sequencing of ZC3H11A-cross-linked RNA showed that ZC3H11A binds to short purine-rich ribonucleotide stretches in cellular and adenoviral transcripts. We show that the RNA-binding property of ZC3H11A is crucial for its function and localization. In ZC3H11A KO cells, the adenovirus fiber mRNA accumulates in the cell nucleus. Our results suggest that ZC3H11A is important for maintaining nuclear export of mRNAs during stress and that several nuclear-replicating viruses take advantage of this mechanism to facilitate their replication.

1 - 14 of 14
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf