Cloning and DNA sequencing of the dextranase inhibitor gene (dei) from Streptococcus sobrinus

Abstract

Some dextranase-deficient (Dex-) mutants of Streptococcus sobrinus UAB66 (serotype g) synthesize a substance which inhibits dextranase activity (S.-Y. Wanda, A. Camilli, H. M. Murchison, and R. Curtiss III, J. Bacteriol. 176:7206-7212, 1994). This substance produced by the Dex- mutant UAB108 was designated dextranase inhibitor (Dei) and identified as a protein. The Dei gene (dei) from UAB108 has been cloned into pACYC184 to yield pYA2651, which was then used to generate several subclones (pYA2653 to pYA2657). The DNA sequence of dei was determined by using Tn5seq1 transposon mutagenesis of pYA2653. The open reading frame of dei is 990 bp long. It encodes a signal peptide of 38 amino acids and a mature Dei protein of 292 amino acids with a molecular weight of 31,372. The deduced amino acid sequence of Dei shows various degrees of similarity with glucosyltransferases and glucan-binding protein and contains A and C repeating units probably involved in glucan binding. Southern hybridization results showed that the dei probe from UAB108 hybridized to the same-size fragment in S. sobrinus (serotype d and g) DNA, to a different-size fragment in S. downei (serotype h) and S. cricetus (serotype a), and not at all to DNAs from other mutans group of streptococci.

Insertional inactivation of the Streptococcus mutans dexA (dextranase) gene results in altered adherence and dextran catabolism

“…Nucleotide sequencing of part of the inactivated gene flanking the inserted plasmid revealed that it encoded a stretch of protein with 56% homology with an internal fragment of the S. sobrinus dextranase recently reported by Wanda & Curtiss (1994). The entire S. mutans dextranase gene sequence has now been determined (Igarashi et al, 1995) and submitted to GenBank (accession number D49430) and there is > 45% overall amino acid homology between this gene and the dextranase gene from S. sobrinus.…”

“…Despite the similarity in sequence, however, it appears that dextranase in S. mutans is regulated in an entirely different way to S. sobrinus, in which a dextranase inhibitor plays a role in controlling activity (Hamelik & McCabe, 1982;Sun et al, 1994;Wellington et al, 1994). No comparable inhibitor has been reported in S. mutans and our investigation has failed to reveal one.…”

Streptococcal Adhesion and Colonization

“…59 S. mutans SJ Glucan (1 ,6-a-linked) Smith et al (1994) Dextranase inhibitor 31 S. sobrinus UAB1 08 Dextran Sun et al (1994) (Dei) ing a salivary receptor. Furthermore, adhesins of differing tion mediated by higher-affinity adhesins (Cowan et al., specificities may allow the bacteria to adhere to bind dif-1986).…”

Sequence Analysis of the Streptococcus mutans Ingbritt dexA Gene Encoding Extracellular Dextranase

“…Although the secretory proteins of oral streptococci such as GTFs, FTF, Dei, and GBP (1,9,35,36,39) usually have a signal peptide at their N terminus, they have no cell wall-anchoring region at the C terminus. DexA is an unusual secretory protein as it has the puta,-tive cell wall-anchoring region at the C terminus as presented in Figs.…”