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Complete nucleotide sequence of type 6 M protein of the group A Streptococcus. Repetitive structure and membrane
Abstract:
The DNA sequence of the gene for type 6 M protein of Streptococcus pyogenes contains two extended tandem repeat regions and one nontandem repeat region. We suggest that the duplication and deletion of these repeats generates the observed diversity in size and sequence among the family of M proteins in the group A streptococci. In addition, the DNA sequence reveals the presence of a 42-amino-acid signal peptide, a region rich in proline that is thought to be located in the cell wall, and a membrane anchor sequence at the carboxyl-terminal end of the protein. Signals similar to the consensus sequences recognized for the initiation of transcription and translation in Gram-positive bacteria have been identified in the DNA sequence. Codon usage is similar to that of other Gram-positive bacteria and significantly different from that of Escherichia coli.
Insights
The Streptococcus pyogenes M protein gene contains repeat regions that likely drive diversity in M protein size and sequence. This study details the gene
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Streptococcus pyogenes is a significant human pathogen.
- M proteins are key virulence factors in Group A Streptococcus, contributing to immune evasion.
- Understanding M protein diversity is crucial for vaccine development and disease control.
Purpose of the Study:
- To determine the DNA sequence of the type 6 M protein gene from Streptococcus pyogenes.
- To investigate the genetic basis for the observed diversity in M protein size and sequence within Group A streptococci.
- To identify key protein domains and regulatory elements within the M protein gene.
Main Methods:
- DNA sequencing of the type 6 M protein gene.
- Bioinformatic analysis of the DNA sequence to identify repeat regions, coding sequences, and regulatory signals.
- Comparison of codon usage with other bacterial species.
Main Results:
- The gene contains two extended tandem repeat regions and one nontandem repeat region.
- A 42-amino-acid signal peptide, a proline-rich cell wall region, and a membrane anchor sequence were identified.
- Consensus sequences for transcription and translation initiation in Gram-positive bacteria were found.
- Codon usage patterns were consistent with Gram-positive bacteria but distinct from Escherichia coli.
Conclusions:
- Duplication and deletion of repeat regions are proposed mechanisms for generating M protein diversity.
- The identified structural features (signal peptide, proline-rich region, anchor) provide insights into M protein function and localization.
- The genetic organization and codon usage suggest evolutionary adaptations specific to Gram-positive bacterial hosts.