| 1. |
- Johanson, U, et al.
(author)
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The dynamic structure of EF-G studied by fusidic acid resistance and internal revertants
- 1996
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In: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836. ; 258:3, s. 32-420
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Journal article (peer-reviewed)abstract
- We have previously identified 20 different fusidic acid-resistant alleles of fusA, encoding mutant forms of the ribosomal translocase EF-G. One of these, P413L, is used here as the starting point in selections for internal revertants, identifying 20 different pseudo-wild-type forms of EF-G. We have also identified two alleles of fusA previously isolated as suppressors of 4.5 S RNA deficiency. All of these mutants are analysed in terms of their effects on the structural dynamics of EF-G. Most mutation conferring fusidic acid-resistance interfere with conformational changes of EF-G, but some may be located at a possible fusidic acid binding site. Revertants of the P413L mutations restore the function of EF-G with or without affecting the level of resistance to fusidic acid. The revertant mutations probably restore the balance between the GDP and GTP conformations of EF-G off the ribosome, and most of them are located close to the interface between the G domain and domain II. The procedure for the isolation of pseudo-wild-type forms of EF-G can be used to direct evolution progressively away from the wild-type while still maintaining the essential functions of EF-G.
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| 2. |
- Johanson, U, et al.
(author)
-
The dynamic structure of EF-G studied by fusidic acid resistance and internal revertants
- 1996
-
In: JOURNAL OF MOLECULAR BIOLOGY. - : ACADEMIC PRESS LTD. - 0022-2836. ; 258:3, s. 420-432
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Journal article (other academic/artistic)abstract
- We have previously identified 20 different fusidic acid-resistant alleles of fusA, encoding mutant forms of the ribosomal translocase EF-G. One of these, P413L, is used here as the starting point in selections for internal revertants, identifying 20 diffe
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| 3. |
- Larsson, A, et al.
(author)
-
Regional cerebral blood flow in normal individuals aged 40, 75 and 88 years studied by 99Tc(m)-d,l-HMPAO SPET.
- 2001
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In: Nuclear medicine communications. - 0143-3636. ; 22:7, s. 741-6
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Journal article (peer-reviewed)abstract
- Age-related changes in cerebral blood flow (CBF) were examined with [99Tc(m)]-d,l-hexamethylpropylene amine oxime (HMPAO), using a single photon emission tomography (SPET) gamma camera system equipped with a high resolution collimator, in 33 normal individuals in three age groups: 40 years old (n = 11), 75 years old (n = 9) and 88 years old (n = 13). A standard activity of 1000 MBq [99Tc(m)]-d,l-HMPAO was administered. Regional CBF (rCBF) (relative to cerebellar counts) was quantified in 28 grey and white matter regions. The mean rCBF of all the regions was 0.80 (95% confidence interval [CI] 0.77-0.83) in 40 year olds, 0.77 (0.74-0.80) in 75 year olds and 0.76 (0.73-0.78) in 88 year olds. rCBF in the hippocampus, angular and cingular gyri, and frontal association and motor cortices was 5-10% lower in the 75 and 88 year olds than in the middle-aged subjects (P < 0.05). The annual reduction in rCBF was 0.10% between the ages of 40 and 75 years and 0.13% between the ages of 75 and 88 years. The reduction in rCBF in the hippocampus rose from 0.14% between the ages of 40 and 75 years to 0.33% between the ages of 75 and 88 years. The mean rCBF in all 33 individuals showed no sex-related differences.
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| 4. |
- Aevarsson, Arnthór, et al.
(author)
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Going to extremes - a metagenomic journey into the dark matter of life
- 2021
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In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968. ; 368:12
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Research review (peer-reviewed)abstract
- The Virus-X-Viral Metagenomics for Innovation Value-project was a scientific expedition to explore and exploit uncharted territory of genetic diversity in extreme natural environments such as geothermal hot springs and deep-sea ocean ecosystems. Specifically, the project was set to analyse and exploit viral metagenomes with the ultimate goal of developing new gene products with high innovation value for applications in biotechnology, pharmaceutical, medical, and the life science sectors. Viral gene pool analysis is also essential to obtain fundamental insight into ecosystem dynamics and to investigate how viruses influence the evolution of microbes and multicellular organisms. The Virus-X Consortium, established in 2016, included experts from eight European countries. The unique approach based on high throughput bioinformatics technologies combined with structural and functional studies resulted in the development of a biodiscovery pipeline of significant capacity and scale. The activities within the Virus-X consortium cover the entire range from bioprospecting and methods development in bioinformatics to protein production and characterisation, with the final goal of translating our results into new products for the bioeconomy. The significant impact the consortium made in all of these areas was possible due to the successful cooperation between expert teams that worked together to solve a complex scientific problem using state-of-the-art technologies as well as developing novel tools to explore the virosphere, widely considered as the last great frontier of life.
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| 5. |
- Aevarsson, A, et al.
(author)
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Ligands to the 2Fe iron-sulfur center in succinate dehydrogenase
- 1988
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In: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 232:2, s. 298-302
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Journal article (peer-reviewed)abstract
- Membrane-bound succinate oxidoreductases are flavoenzymes containing one each of a 2Fe, a 3Fe and a 4Fe iron-sulfur center. Amino acid sequence homologies indicate that all three centers are located in the Ip (B) subunit. From polypeptide and gene analysis of Bacillus subtillis succinate dehydrogenase-defective mutants combined with earlier EPR spectroscopic data, we show that four conserved cysteine residues in the first half of Ip are the ligands to the [2Fe-2S] center. These four residues have previously been predicted to be the ligands. Our results also suggest that the N-terminal part of B. subtilis Ip constitutes a domain which can incorporate separately the 2Fe center and interact with Fp, the flavin-containing subunit of the dehydrogenase.
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| 6. |
- Ahlqvist, Josefin, et al.
(author)
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Crystal structure and initial characterization of a novel archaeal-like Holliday junction-resolving enzyme from Thermus thermophilus phage Tth15-6
- 2022
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In: Acta crystallographica. Section D, Structural biology. - 2059-7983. ; 78:Pt 2, s. 212-227
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Journal article (peer-reviewed)abstract
- This study describes the production, characterization and structure determination of a novel Holliday junction-resolving enzyme. The enzyme, termed Hjc_15-6, is encoded in the genome of phage Tth15-6, which infects Thermus thermophilus. Hjc_15-6 was heterologously produced in Escherichia coli and high yields of soluble and biologically active recombinant enzyme were obtained in both complex and defined media. Amino-acid sequence and structure comparison suggested that the enzyme belongs to a group of enzymes classified as archaeal Holliday junction-resolving enzymes, which are typically divalent metal ion-binding dimers that are able to cleave X-shaped dsDNA-Holliday junctions (Hjs). The crystal structure of Hjc_15-6 was determined to 2.5 Å resolution using the selenomethionine single-wavelength anomalous dispersion method. To our knowledge, this is the first crystal structure of an Hj-resolving enzyme originating from a bacteriophage that can be classified as an archaeal type of Hj-resolving enzyme. As such, it represents a new fold for Hj-resolving enzymes from phages. Characterization of the structure of Hjc_15-6 suggests that it may form a dimer, or even a homodimer of dimers, and activity studies show endonuclease activity towards Hjs. Furthermore, based on sequence analysis it is proposed that Hjc_15-6 has a three-part catalytic motif corresponding to E-SD-EVK, and this motif may be common among other Hj-resolving enzymes originating from thermophilic bacteriophages.
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| 7. |
- Ahlqvist, Josefin, et al.
(author)
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Crystal structure of DNA polymerase I from Thermus phage G20c
- 2022
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In: Acta crystallographica. Section D, Structural biology. - 2059-7983. ; 78:Pt 11, s. 1384-1398
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Journal article (peer-reviewed)abstract
- This study describes the structure of DNA polymerase I from Thermus phage G20c, termed PolI_G20c. This is the first structure of a DNA polymerase originating from a group of related thermophilic bacteriophages infecting Thermus thermophilus, including phages G20c, TSP4, P74-26, P23-45 and phiFA and the novel phage Tth15-6. Sequence and structural analysis of PolI_G20c revealed a 3'-5' exonuclease domain and a DNA polymerase domain, and activity screening confirmed that both domains were functional. No functional 5'-3' exonuclease domain was present. Structural analysis also revealed a novel specific structure motif, here termed SβαR, that was not previously identified in any polymerase belonging to the DNA polymerases I (or the DNA polymerase A family). The SβαR motif did not show any homology to the sequences or structures of known DNA polymerases. The exception was the sequence conservation of the residues in this motif in putative DNA polymerases encoded in the genomes of a group of thermophilic phages related to Thermus phage G20c. The structure of PolI_G20c was determined with the aid of another structure that was determined in parallel and was used as a model for molecular replacement. This other structure was of a 3'-5' exonuclease termed ExnV1. The cloned and expressed gene encoding ExnV1 was isolated from a thermophilic virus metagenome that was collected from several hot springs in Iceland. The structure of ExnV1, which contains the novel SβαR motif, was first determined to 2.19 Å resolution. With these data at hand, the structure of PolI_G20c was determined to 2.97 Å resolution. The structures of PolI_G20c and ExnV1 are most similar to those of the Klenow fragment of DNA polymerase I (PDB entry 2kzz) from Escherichia coli, DNA polymerase I from Geobacillus stearothermophilus (PDB entry 1knc) and Taq polymerase (PDB entry 1bgx) from Thermus aquaticus.
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