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Identification of a divergent M protein gene and an M protein-related gene family in Streptococcus pyogenes serotype
1Department of Microbiology, University of Minnesota, Minneapolis 55455.
Abstract:
The antigenically variant M protein of Streptococcus pyogenes enhances virulence by promoting resistance to phagocytosis. The serum opacity factor (OF), produced by a subset of M serotypes, is also antigenically variant, and its antigenic variability exactly parallels that of M protein. OF-positive and OF-negative streptococci are also phenotypically distinguishable by a number of other criteria. In order to study the differences between OF-positive and OF-negative streptococci, we cloned and sequenced the type 49 M protein gene (emm49), the first to be cloned from an OF-positive strain. This gene showed evolutionary divergence from the OF-negative M protein genes studied previously. Furthermore, emm49 was part of a gene family, in contrast to the single-copy nature of previously characterized M protein genes.
Insights
Streptococcus pyogenes M protein enhances virulence. This study cloned and sequenced the OF-positive emm49 gene, revealing evolutionary divergence and a gene family structure distinct from OF-negative strains.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Streptococcus pyogenes M protein is antigenically variant, enhancing virulence by resisting phagocytosis.
- Serum opacity factor (OF) is also antigenically variant, with variability paralleling M protein.
- OF-positive and OF-negative strains exhibit distinct phenotypic characteristics.
Purpose of the Study:
- To investigate the genetic differences between OF-positive and OF-negative Streptococcus pyogenes strains.
- To clone and sequence the emm49 gene from an OF-positive strain.
Main Methods:
- Cloning of the type 49 M protein gene (emm49) from an OF-positive Streptococcus pyogenes strain.
- DNA sequencing of the emm49 gene.
- Comparative analysis of emm49 with previously characterized OF-negative M protein genes.
Main Results:
- The emm49 gene sequence demonstrated evolutionary divergence from OF-negative M protein genes.
- emm49 was found to be part of a gene family.
- Previously characterized M protein genes were typically single-copy.
Conclusions:
- The genetic makeup of OF-positive M protein genes, exemplified by emm49, differs significantly from OF-negative strains.
- The presence of emm49 within a gene family suggests a distinct evolutionary path for OF-positive Streptococcus pyogenes.
- These findings contribute to understanding the genetic basis of Streptococcus pyogenes virulence and phenotypic variation.