| 1. |
- Ben Nasr, Abdelhakim, et al.
(författare)
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Streptokinase activates plasminogen bound to human group C and group G streptococci through M-like proteins
- 1994
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Ingår i: European Journal of Biochemistry. - 0014-2956. ; 222:2, s. 76-267
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Tidskriftsartikel (refereegranskat)abstract
- An ability to interact with plasminogen or plasmin could provide micro-organisms with a mechanism for invasion. Thus, group A, C and G streptococci secrete streptokinase which binds and activates plasminogen. Some streptococci also express surface structures which bind plasminogen without causing its activation. Plasminogen-binding surface proteins were extracted from one group C and one group G streptococcal isolate. Both proteins were found to bind plasmin, fibrinogen and serum albumin in addition to plasminogen. Gene fragments encoding the streptococcal proteins were amplified by PCR and were subsequently cloned and expressed in Escherichia coli. DNA sequence determination revealed for both genes open reading frames encoding proteins which contained repetitive domains and a carboxyl-terminal unrepeated region that were typical of M and M-like proteins. Though the amino-terminal regions of the group C and G streptococcal proteins demonstrated a rather high overall similarity between themselves, they were not similar to the variable regions of other M-like proteins with one exception: there was a 46% identity between the first 22 amino acids of the group G streptococcal protein and the corresponding sequence of PAM, the plasminogen-binding M-like protein of type M53 group A streptococci. Like the proteins extracted from the streptococci, the recombinant proteins bound plasminogen, fibrinogen and albumin. The three plasma proteins bound to separate sites on the streptococcal M-like proteins. Plasminogen bound by the group C and G streptococcal proteins was readily activated by streptokinase, providing evidence for a functional link between the secreted plasminogen-activator and proteins exposed on the bacterial surface.
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| 2. |
- Frick, Inga-Maria, et al.
(författare)
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Protein H--a surface protein of Streptococcus pyogenes with separate binding sites for IgG and albumin
- 1994
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 12:1, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Protein H, a molecule expressed at the surface of some strains of Streptococcus pyogenes, has affinity for the constant (IgGFc) region of immunoglobulin (Ig) G. In absorption experiments with human plasma, protein H-sepharose could absorb not only IgG but also albumin from plasma. The affinity constant for the reaction between albumin and protein H was 7.8 x 10(9) M-1, which is higher than the affinity between IgG and protein H (Ka = 1.6 x 10(9) M-1). Fragments of protein H were generated with deletion plasmids and polymerase chain reaction (PCR) technology. Using these fragments in various protein-protein interaction assays, the binding of albumin was mapped to three repeats (C1-C3) in the C-terminal half of protein H. On the albumin molecule, the binding site for protein H was found to overlap the site for protein G, another albumin- and IgGFc-binding bacterial surface protein. Also IgGFc-binding could be mapped with the protein H fragments and the region was found N-terminally of the C repeats. A synthetic peptide (25 amino acid residues long) based on a sequence in this region was shown to inhibit the binding of protein H to immobilized IgG or IgGFc. This sequence was not found in previously described IgGFc-binding proteins. However, two other cell surface proteins of S. pyogenes exhibited highly homologous regions. The results identify IgGFc- and albumin-binding regions of protein H and further define and emphasize the convergent evolution among bacterial surface proteins interacting with human plasma proteins.
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| 3. |
- Savic, B, et al.
(författare)
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Evaluation of polymerase chain reaction, tuberculostearic acid analysis, and direct microscopy for the detection of Mycobacterium tuberculosis in sputum
- 1992
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Ingår i: Journal of Infectious Diseases. - 1537-6613. ; 166:5, s. 1177-1180
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Tidskriftsartikel (refereegranskat)abstract
- Tuberculosis remains a major global cause of morbidity and mortality. There is an urgent need for improved bacteriologic diagnosis of Mycobacterium tuberculosis infection. Three methods for rapid identification of M. tuberculosis in sputum samples (direct microscopy, gas chromatography-mass spectrometry [GC-MS], and polymerase chain reaction [PCR]), were compared with culture on Lowenstein-Jensen medium. Growth of M. tuberculosis was observed in 38 of 145 sputum samples. Detection of acid-fast bacilli by direct microscopy gave a sensitivity of 66% and a specificity of 100%. Detection of tuberculostearic acid by GC-MS gave a sensitivity of 55% and a specificity of 87%. Amplification by PCR of a fragment of the insertion sequence IS6110 gave a sensitivity of 95% and a specificity of 93% compared with culture and a corrected specificity of 99% compared with both culture and clinical data. This study indicates that PCR can be adapted for clinical use and is the method of choice for rapid diagnosis of pulmonary tuberculosis.
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| 4. |
- Sjöbring, Ulf, et al.
(författare)
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Polymerase chain reaction for detection of Mycobacterium tuberculosis
- 1990
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Ingår i: Journal of Clinical Microbiology. - 1098-660X. ; 28:10, s. 2200-2204
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Tidskriftsartikel (refereegranskat)abstract
- A polymerase chain reaction for the specific detection of mycobacteria belonging to the Mycobacterium tuberculosis complex was developed. Using a single primer pair derived from the nucleotide sequence of protein antigen b of M. tuberculosis, we achieved specific amplification of a 419-base-pair DNA fragment in M. tuberculosis and M. bovis. After DNA was extracted from mycobacteria by using a simple, safe lysis procedure, we detected the 419-base-pair sequence in samples containing few mycobacteria. Preliminary data suggested that this technique could be applied to clinical specimens for early and specific diagnosis of tuberculosis.
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