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Publication Abstract from PubMed

The genome sequence of the oral pathogen Streptococcus mutans, predicts the presence of two putative polysaccharide deacetylases. The first, designated PgdA in this paper, shows homology to the catalytic domains of peptidoglycan deacetylases from Streptococcus pneumoniae and Listeria monocytogenes, that are both thought to be involved in the bacterial defense mechanism against human mucosal lysozyme, and are part of the CAZY family 4 carbohydrate esterases. S. mutans cells in which the pgdA gene was deleted displayed a different colony texture and a slightly increased cell surface hydrophobicity, yet did not become hypersensitive to lysozyme as shown previously for S. pneumoniae. To understand this apparent lack of activity, the high resolution X-ray structure of S. mutans PgdA was determined, which showed the typical CE4 esterase fold, with metal bound in a His-His-Asp triad. Analysis of the protein surface showed that an extended groove lined with aromatic residues is orientated towards the active site residues. The protein exhibited metal dependent de-N-acetylase activity towards a hexamer of N-acetylglucosamine. No activity was observed towards shorter chitooligosaccharides or a synthetic peptidoglycan tetrasaccharide. In agreement with the lysozyme data this would suggest that S. mutans PgdA does not act on peptidoglycan but on an as yet unidentified polysaccharide within the bacterial cell surface. Strikingly, the pgdA knock-out strain showed a significant increase in aggregation/agglutination by salivary agglutinin, in agreement with this gene acting as a deacetylase of a cell surface glycan.

Streptococcus mutans SMU.623c codes for a functional, metal dependent polysaccharide deacetylase that modulates interactions with salivary agglutinin.,Deng DM, Urch JE, Ten Cate JM, Rao VA, van Aalten DM, Crielaard W J Bacteriol. 2008 Oct 31. PMID:18978064^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.