| 1. |
- Ben Nasr, Abdelhakim, et al.
(author)
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Absorption of kininogen from human plasma by Streptococcus pyogenes is followed by the release of bradykinin
- 1997
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In: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 326:3, s. 657-660
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Journal article (peer-reviewed)abstract
- H-kininogen (high-molecular-mass kininogen, HK) is the precursor of the vasoactive peptide hormone bradykinin (BK). Previous work has demonstrated that HK binds to Streptococcus pyogenes through M-proteins, fibrous surface proteins and important virulence factors of these bacteria. Here we find that M-protein-expressing bacteria absorb HK from human plasma. The HK bound to the bacteria was found to be cleaved, and analysis of the degradation pattern suggested that the cleavage of HK at the bacterial surface is associated with the release of BK. Moreover, addition of activated plasma prekallikrein to bacteria preincubated with human plasma, resulted in BK release. This mechanism, by which a potent vasoactive and proinflammatory peptide is generated at the site of infection, should influence the host-parasite relationship during S. pyogenes infections.
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| 2. |
- Ben Nasr, Abdelhakim, et al.
(author)
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Assembly of human contact phase factors and release of bradykinin at the surface of curli-expressing Escherichia coli
- 1996
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In: Molecular Microbiology. - 1365-2958. ; 20:5, s. 35-927
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Journal article (peer-reviewed)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.
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