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Characterization of a gene coding for a type IIo bacterial IgG-binding protein
M D Boyle1, J Weber-Heynemann, R Raeder
1Department of Microbiology, Medical College of Ohio, Toledo 43699-0008, USA.
Molecular Immunology
|June 1, 1995
Summary
Group A streptococci express two IgG-binding protein classes. Researchers identified the emm-like (emmL) gene product as the second class, binding various IgG types and other proteins.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Group A streptococci (GAS) express surface proteins that bind immunoglobulin G (IgG).
- Two distinct antigenic classes of these IgG-binding proteins are known.
- One class is recognized by antibodies against the fcrA gene product (FcRA).
Purpose of the Study:
- To identify the immunogen responsible for the second antigenic class of GAS IgG-binding proteins.
- To characterize the properties of this newly identified protein.
Main Methods:
- Cloning and expression of the emm-like (emmL) gene from a specific M serotype 55 GAS isolate (A928) in E. coli.
- Analysis of the recombinant protein's molecular weight and binding characteristics.
- Sequence analysis of the emmL55 gene.
Main Results:
- The emmL55 gene product is an approximately 58,000 M(r) protein.
- This recombinant protein exhibited non-immune binding to human IgG subclasses (IgG1-4) and IgG from multiple animal species (horse, rabbit, pig).
- The protein also showed reactivity with human serum albumin and fibrinogen.
- Sequence analysis confirmed the emmL55 gene as a typical class I emm-like gene.
Conclusions:
- The emm-like (emmL) gene product represents the second antigenic class of IgG-binding proteins in group A streptococci.
- This protein, designated type IIo, possesses broad IgG-binding capabilities and interacts with host proteins like albumin and fibrinogen.
- The findings contribute to understanding GAS virulence mechanisms and host-pathogen interactions.