The fibrinogen-binding protein (FgBP) of Streptococcus equi subsp. equi additionally binds IgG and contributes to virulence in a mouse model.
Abstract: The major cell-wall-associated protein of the equine pathogen Streptococcus equi subsp. equi is an M-like fibrinogen-binding protein (FgBP) which binds equine fibrinogen (Fg) avidly, through residues located at the extreme N-terminus of the molecule. In this study, it is shown that FgBP additionally binds equine IgG-Fc. When tested against polyclonal IgG from ten other animal species, it was found that FgBP binds human, rabbit, pig and cat IgG, but does not bind mouse, rat, goat, sheep, cow or chicken IgG. Through the use of a panel of recombinant FgBP truncates containing defined deletions of sequence, it was shown that residues in the central regions of FgBP are important in IgG binding. An fbp knockout mutant which does not express FgBP on the cell surface was also constructed. Mutant cells failed to autoaggregate, bound no detectable equine Fg or IgG-Fc, were rapidly killed in horse blood, and showed greatly decreased virulence in a mouse model. Results suggest that FgBP is the major surface structure responsible for binding either Fg or IgG, that the molecule has pronounced antiphagocytic properties, and that it is a likely factor contributing to the virulence of wild-type S. equi subsp. equi.
Publication Date: 2001-12-12 PubMed ID: 11739763DOI: 10.1099/00221287-147-12-3311Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study aims at exploring the role of Fibrinogen-binding protein (FgBP) in the equine pathogen, Streptococcus equi. It uncovers that FgBP not only interacts with horse fibrinogen but also with specific IgG subclasses from multiple species, suggesting its possible function in the pathogen’s virulence.
Overview of the Study
- The primary focus of the study was the Fibrinogen-binding protein (FgBP) of a horse pathogen, Streptococcus equi subsp. equi. This protein is heavily associated with the cell-wall of the pathogen and is known to bind very strongly with horse fibrinogen, especially residues at the N-terminus part of the protein molecule.
- The study exhibits that FgBP also actively interacts with the IgG-Fc section of horse antibodies.
- Moreover, when tested with polyclonal IgG from other animal species, it was found that FgBP also interacts with rabbit, pig, human, and cat IgG but displayed no binding with the IgG from mouse, rat, goat, sheep, cow, or chicken.
Experimental Design and Results
- The researchers employed a set of recombinant FgBP truncates with defined deletions of sequence to demonstrate that the central sections of the FgBP protein are crucial for IgG binding.
- A mutant of the fbp gene was also constructed, which led to off the surface expression of FgBP. The mutant cells presented multiple peculiar characteristics: they couldn’t autoaggregate, displayed no detectable binding with horse fibrinogen or IgG-Fc, were quickly killed in horse blood, and displayed reduced virulence in a murine model.
Implication of the Findings
- The findings indicate that FgBP is the main surface structure that manages the binding of either fibrinogen or IgG. It has strong antiphagocytic properties suggesting its significant role in preventing the pathogen from being destroyed by host cells.
- Additionally, the study also shows that FgBP contributes to the virulence of Streptococcus equi subsp. equi, signifying the protein’s crucial role in the bacteria’s strategy to invade and persist in the host.
Cite This Article
APA
Meehan M, Lynagh Y, Woods C, Owen P.
(2001).
The fibrinogen-binding protein (FgBP) of Streptococcus equi subsp. equi additionally binds IgG and contributes to virulence in a mouse model.
Microbiology (Reading), 147(Pt 12), 3311-3322.
https://doi.org/10.1099/00221287-147-12-3311 Publication
Researcher Affiliations
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
MeSH Terms
- Animals
- Bacterial Proteins / metabolism
- Binding Sites
- Blood / microbiology
- Carrier Proteins / metabolism
- Carrier Proteins / pharmacology
- Fibrinogen / metabolism
- Horse Diseases / microbiology
- Horses
- Immunoglobulin G / metabolism
- Mice
- Phagocytosis / drug effects
- Protein Binding
- Protein Structure, Tertiary
- Respiratory Tract Infections / veterinary
- Streptococcus equi / pathogenicity
Citations
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- Pickering AC, Fitzgerald JR. The Role of Gram-Positive Surface Proteins in Bacterial Niche- and Host-Specialization. Front Microbiol 2020;11:594737.
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