Sequence analysis of the Streptococcus mutans Ingbritt dexA gene encoding extracellular dextranase

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Streptococcus mutans is a key pathogen in dental caries.
• Dextranase (dexA) plays a role in carbohydrate metabolism and biofilm formation.
• Understanding the genetic basis of dextranase is crucial for developing targeted interventions.

Purpose of the Study:

• To determine the complete nucleotide sequence of the dextranase gene (dexA) and its flanking regions in Streptococcus mutans Ingbritt (serotype c).
• To analyze the genetic features of dexA, including its open reading frame, promoter, and potential regulatory elements.
• To compare the deduced amino acid sequence of the S. mutans dextranase (DexA) with homologous proteins from other streptococci.

Main Methods:

• DNA sequencing of the dexA gene and flanking chromosomal regions.
• Bioinformatic analysis to identify the open reading frame, stop codon, ribosome-binding site, and promoter.
• Sequence homology searches and comparison of nucleotide and amino acid sequences with related genes/proteins.

Main Results:

• The complete nucleotide sequence of dexA (2,550 bp open reading frame) and flanking regions (3,747 bp total) was determined.
• Putative regulatory elements including a ribosome-binding site and promoter were identified.
• The deduced 850-amino acid DexA protein showed 57.8% nucleotide and 47.0% amino acid homology to Streptococcus sobrinus dextranase, primarily in the N-terminal region.
• The C-terminus of DexA possesses a characteristic structure found in surface-associated Gram-positive bacterial proteins and extracellular enzymes.

Conclusions:

• The genetic and structural characterization of the Streptococcus mutans dextranase (dexA) provides insights into its potential function and regulation.
• The identified homologies suggest conserved functional domains within dextranases of related oral streptococci.
• The unique C-terminal structure of DexA may be involved in protein localization or interaction with the cell surface or extracellular matrix.