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Sequence Analysis of the Streptococcus mutans Ingbritt dexA Gene Encoding Extracellular Dextranase
Author(s) -
Igarashi Takeshi,
Yamamoto Ayako,
Goto Nobuichi
Publication year - 1995
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.1995.tb03282.x
Subject(s) - dextranase , streptococcus sobrinus , streptococcus mutans , biology , nucleic acid sequence , open reading frame , amino acid , biochemistry , peptide sequence , ribosomal binding site , microbiology and biotechnology , consensus sequence , gene , genetics , enzyme , bacteria , ribosome , rna
The complete nucleotide sequence (3,747 bp) of the dextranase gene ( dexA ) and flanking regions of the chromosome of Streptococcus mutans Ingbritt (serotype c) were determined. The open reading frame for dexA was 2,550 bp, ending with a stop codon TGA. A putative ribosome‐binding site, promoter preceding the start codon, and potential stem‐loop structure were identified. The presumed dextranase protein (DexA) consisting of 850 amino acids was estimated to have a molecular size of 94,536 Da and a pI of 4.79. The nucleotide sequence and the deduced amino acid sequences of S. mutans dexA exhibited homologies of 57.8% and 47.0%, respectively, to those of Streptococcus sobrinus dex . The homologous region of dex of S. sobrinus was in the N‐terminal half. The C terminus of DexA consisted of a hexapeptide LPQTGD, followed by 7 charged amino acids, 21 amino acids with a strongly hydrophobic character, and a charged hexapeptide tail, which have been reported as a common structure of C termini of not only the surface‐associated proteins of Gram‐positive cocci but also the extracellular enzymes such as β‐fructosidase of S. mutans and dextranase of S. sobrinus . The DexA protein had no significant homology with the glucosyltransferases, the glucan‐binding protein, or the dextranase inhibitor of mutans streptococci.