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Sökning: WFRF:(Olsén Arne)

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  • Allhorn, Maria, et al. (författare)
  • EndoS from Streptococcus pyogenes is hydrolyzed by the cysteine proteinase SpeB and requires glutamic acid 235 and tryptophans for IgG glycan-hydrolyzing activity
  • 2008
  • Ingår i: BMC Microbiology. - : BioMed Central (BMC). - 1471-2180. ; 8:1
  • Tidskriftsartikel (refereegranskat)abstract
    • ABSTRACT: BACKGROUND: The endoglycosidase EndoS and the cysteine proteinase SpeB from the human pathogen Streptococcus pyogenes are functionally related in that they both hydrolyze IgG leading to impairment of opsonizing antibodies and thus enhance bacterial survival in human blood. In this study, we further investigated the relationship between EndoS and SpeB by examining their in vitro temporal production and stability and activity of EndoS. Furthermore, theoretical structure modeling of EndoS combined with site-directed mutagenesis and chemical blocking of amino acids was used to identify amino acids required for the IgG glycan-hydrolyzing activity of EndoS. RESULTS: We could show that during growth in vitro S. pyogenes secretes the IgG glycan-hydrolyzing endoglycosidase EndoS prior to the cysteine proteinase SpeB. Upon maturation SpeB hydrolyzes EndoS that then loses its IgG glycan-hydrolyzing activity. Sequence analysis and structural homology modeling of EndoS provided a basis for further analysis of the prerequisites for IgG glycan-hydrolysis. Site-directed mutagenesis and chemical modification of amino acids revealed that glutamic acid 235 is an essential catalytic residue, and that tryptophan residues, but not the abundant lysine or the single cysteine residues, are important for EndoS activity. CONCLUSIONS: We present novel information about the amino acid requirements for IgG glycan-hydrolyzing activity of the immunomodulating enzyme EndoS. Furthermore, we show that the cysteine proteinase SpeB processes/degrades EndoS and thus emphasize the importance of the SpeB as a degrading/processing enzyme of proteins from the bacterium itself.
  • Ben Nasr, Abdelhakim, et al. (författare)
  • Assembly of human contact phase factors and release of bradykinin at the surface of curli-expressing Escherichia coli
  • 1996
  • Ingår i: Molecular Microbiology. - : Wiley-Blackwell. - 1365-2958. ; 20:5, s. 35-927
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous work has demonstrated that most strains of the human pathogen Streptococcus pyogenes bind kininogens through M protein, a fibrous surface protein and virulence determinant. Here we find that strains of several other pathogenic bacterial species, both Gram-positive and Gram-negative, isolated from patients with sepsis, also bind kininogens, especially kininogen (HK). The most pronounced interaction was seen between HK and Escherichia coli. Among clinical isolates of E. coli, the majority of the enterohaemorrhagic, enterotoxigenic, and sepsis strains, but none of the enteroinvasive and enteropathogenic strains, bound HK. Binding of HK to E. coli correlated with the expression of curli, another fibrous bacterial surface protein, and the binding of HK to purified curli was specific, saturable, and of high affinity; Ka = 9 x 10(7) M-1. Other contact phase proteins such as factor XI, factor XII, and prekallikrein bound to curliated E. coli, but not to an isogenic curli-deficient mutant strain, suggesting that contact phase activation may occur at the surface of curliated bacteria. Kininogens are also precursor molecules of the vasoactive kinins. When incubated with human plasma, curli-expressing bacteria absorbed HK. Addition of purified plasma kallikrein to the HK-loaded bacteria resulted in a rapid and efficient release of bradykinin from surface-bound HK. The assembly of contact phase factors at the surface of pathogenic bacteria and the release of the potent proinflammatory and vasoactive peptide bradykinin, should have a major impact on the host-microbe relationship and may contribute to bacterial pathogenicity and virulence.
  • Bryllert, Tomas, et al. (författare)
  • 11% efficiency 100 GHz InP-based heterostructure barrier varactor quintupler
  • 2005
  • Ingår i: Electronics Letters. - : IEE. ; 41:3, s. 131-132
  • Tidskriftsartikel (refereegranskat)abstract
    • A record conversion efficiency of 11.4% at 100 GHz using a heterostructure barrier varactor (HBV) quintupler is demonstrated. The quintupler is based on a microstrip circuit mounted in a full-height crossed-waveguide block. The nonlinear element consists of a planar HBV diode fabricated in InGaAs=InAlAs=AlAs epitaxial layers on an InP substrate.
  • Bryllert, Tomas, 1974, et al. (författare)
  • A broadband heterostructure barrier varactor tripler source
  • 2010
  • Ingår i: 2010 IEEE MTT-S International Microwave Symposium (MTT). - 0149-645X. - 9781424460571 ; , s. 344-347
  • Konferensbidrag (refereegranskat)abstract
    • We present the first demonstration of a broadband Heterostructure Barrier Varactor tripler, designed to cover a major part of the WR-8 waveguide band. The source comprises a waveguide housing, a six-barrier InP-HBV diode flip-chip mounted on an AlN microstrip filter circuit. The conversion loss 3-dB bandwidth was measured to 17 % at a center frequency of 112 GHz. The maximum output power was more than 15 mW for an input power of 300 mW. There are no mechanical tuners or DC-bias, which simplifies assembly and allows for ultra-compact design.
  • Bryllert, Tomas, 1974, et al. (författare)
  • A monolithic 280 GHz HBV frequency tripler
  • 2010
  • Ingår i: IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide. - 9781424466573
  • Konferensbidrag (refereegranskat)abstract
    • We present the design and measurements of a Heterostructure Barrier Varactor based frequency tripler for 280 GHz. The tripler is fabricated as a monolithic circuit on an InP substrate, including the input and output waveguide probes. Several circuit versions for input power levels between 100 mW and 1W have been designed. © 2010 IEEE.
  • Collin, Mattias, et al. (författare)
  • Effect of SpeB and EndoS from Streptococcus pyogenes on human immunoglobulins
  • 2001
  • Ingår i: Infection and Immunity. - : American Society for Microbiology. - 1098-5522. ; 69:11, s. 7187-7189
  • Tidskriftsartikel (refereegranskat)abstract
    • Streptococcus pyogenes secretes a specific immunoglobulin G (IgG)-protease, SpeB, as well as the IgG glycan-hydrolyzing enzyme EndoS. Here we show that SpeB also degrades IgA, IgM, IgD, and IgE. We also show that EndoS only hydrolyzes the glycan moiety on native but not denatured IgG. Thus, SpeB has a broad immunoglobulin-degrading activity, while EndoS is highly specific for IgG.
  • Collin, Mattias, et al. (författare)
  • EndoS, a novel secreted protein from Streptococcus pyogenes with endoglycosidase activity on human IgG
  • 2001
  • Ingår i: EMBO Journal. - : Oxford University Press. - 1460-2075. ; 20:12, s. 3046-3055
  • Tidskriftsartikel (refereegranskat)abstract
    • Streptococcus pyogenes is an important human pathogen that selectively interacts with proteins involved in the humoral defense system, such as immunoglobulins and complement factors. In this report we show that S.pyogenes has the ability to hydrolyze the chitobiose core of the asparagine-linked glycan on immuno globulin G (IgG) when bacteria are grown in the presence of human plasma. This activity is associated with the secretion of a novel 108 kDa protein denoted EndoS. EndoS has endoglycosidase activity on purified soluble IgG as well as IgG bound to the bacterial surface. EndoS is required for the activity on IgG, as an isogenic EndoS mutant could not hydrolyze the glycan on IgG. In addition, we show that the secreted streptococcal cysteine proteinase SpeB cleaves IgG in the hinge region in a papain-like manner. This is the first example of an endoglycosidase produced by a bacterial pathogen that selectively hydrolyzes human IgG, and reveals a novel mechanism which may contribute to S.pyogenes pathogenesis.
  • Collin, Mattias, et al. (författare)
  • Generation of a mature streptococcal cysteine proteinase is dependent on cell wall-anchored M1 protein
  • 2000
  • Ingår i: Molecular Microbiology. - : Wiley-Blackwell. - 1365-2958. ; 36:6, s. 1306-1318
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present study, we have generated a mutant strain of Streptococcus pyogenes, MC25, which lacks M protein on its surface, and we demonstrate that this strain is unable to generate a mature 28 kDa cysteine proteinase. Furthermore, we show that S. pyogenes bacteria of M1 serotype are dependent on cell wall-anchored M protein to cleave the secreted zymogen into a mature cysteine proteinase. We also show that MC25 secretes a 40 kDa zymogen, having a conformation different from that secreted by wild-type bacteria. We provide data showing that the cleavage site is not blocked but, presumably, the active site is. This suggests that M protein, when anchored to the cell wall, is involved in the unfolding of the zymogen and generation of a mature cysteine proteinase that can be activated under reducing conditions. Our data add new aspects to the interaction between two important virulence factors of S. pyogenes, the streptococcal cysteine proteinase and M protein.
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