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- Davies, Julia, et al.
(författare)
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Identification of novel LPXTG-linked surface proteins from Streptococcus gordonii
- 2009
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 155, s. 1977-1988
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Tidskriftsartikel (refereegranskat)abstract
- Surface adhesion plays an essential part in the survival of the commensal organism Streptococcus gordonii in the oral cavity as well as during opportunistic infections such as endocarditis. At least two types of cell surface protein involved in adhesion are found on the surface of Gram-positive bacteria: those anchored via an LPXTG motif by the enzyme sortase A (SrtA) and those associated with the cell surface by, as yet, unknown mechanisms. In srtA(-) mutants, LPXTG-containing proteins have been shown to be released rather than cross-linked to the cell wall. We have therefore used 2D gel electrophoresis of released proteins from an srtA(-) mutant as well as the wild-type strain, followed by peptide identification by MS, to identify a set of novel proteins predicted to be present on the surface of S. gordonii DL1. This includes two large LPXTG-linked proteins (SGO_0707 and SGO_1487), which both contain tandemly repeated sequences similar to those present in known fibrillar adhesins. A 5'-nucleotidase and a protein with a putative collagen-binding domain, both containing LPXTG motifs, were also identified. Anchorless proteins with known chaperone, stress response and elongation factor functions, apparently responsible for bacterial binding to keratinocytes and saliva-coated surfaces in the absence of the LPXTG-linked adhesins, were also associated with the cell surface. These data reveal a range of proteins to be present on the S. gordonii DL1 cell surface, the expression of which plays an important role in adhesion to epithelia and which represent likely candidates for novel virulence factors in S. gordonii.
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- Wickström, Claes, et al.
(författare)
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Proteolytic degradation of human salivary MUC5B by dental biofilms.
- 2009
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872.
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Tidskriftsartikel (refereegranskat)abstract
- The degradation of complex substrates, like salivary mucins, requires an arsenal of glycosidases and proteases to sequentially degrade the oligosaccharides and polypeptide backbone. MUC5B is a complex oligomeric glycoprotein, heterogeneous in molecular mass (14-40 x 106 Da), with a diverse repertoire of oligosaccharides, differing in composition and charge. The aim of this study was to investigate whether proteolytic degradation of the mucin polypeptide backbone could be identified and if cooperation of dental biofilm bacteria was required. Cooperative bacterial-mediated proteolysis of MUC5B was determined by comparing individual and mixed consortia of strains isolated from supragingival plaque and freshly harvested supragingival plaque. Proteolytic activity was analyzed using fluorescent labelled substrate and by visualizing mucin degradation by SDS-PAGE. Dental plaque degraded the polypeptide backbone of the salivary MUC5B mucin. The mucin also was degraded by a specific consortium of isolated species from supragingival plaque, although individual species and other consortia did not. Select bacteria in supragingival dental plaque, therefore, cooperate as a consortium to proteolyze human salivary MUC5B and hydrolyze glycosides.
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