Document Detail

Sialylation of group B streptococcal capsular polysaccharide is mediated by cpsK and is required for optimal capsule polymerization and expression.
MedLine Citation:
PMID:  15968073     Owner:  NLM     Status:  MEDLINE    
Several bacterial pathogens have evolved the means to escape immune detection by mimicking host cell surface carbohydrates that are crucial for self/non-self recognition. Sialic acid, a terminal residue on these carbohydrates, inhibits activation of the alternate pathway of complement by recruiting the immune modulating molecule factors H, I, and iC3b. Sialylation of capsular polysaccharide (CPS) is important for virulence of group B streptococci (GBS), a significant human pathogen. We previously reported that cpsK, a gene within the cps locus of type III GBS, could complement a sialyltransferase deficient lst mutant of Haemophilus ducreyi, implicating its role in sialylation of the GBS capsule. To explore the function of cpsK in GBS capsule production, we created a mutant in cpsK. Immunoblot analysis and enzyme-linked immunosorbent assay using anti-type III CPS antisera demonstrated that the mutant CPS did not contain sialic acid. This was confirmed by high-performance liquid chromatography after mild acid hydrolysis of the CPS. Although increased CPS chain length was seen for this strain, CPS production was <20% of the parental isolate. An episomal cpsK copy restored synthesis of sialo-CPS to wild-type levels. These data support our hypothesis that cpsK encodes the GBS CPS sialyltransferase and provide further evidence that lack of CPS oligosaccharide sialylation reduces the amount of CPS expressed on the cell surface. These observations also imply that one or more of the components involved in synthesis or transport of oligosaccharide repeating units requires a sialo-oligosaccharide for complete activity.
D O Chaffin; L M Mentele; C E Rubens
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of bacteriology     Volume:  187     ISSN:  0021-9193     ISO Abbreviation:  J. Bacteriol.     Publication Date:  2005 Jul 
Date Detail:
Created Date:  2005-06-21     Completed Date:  2005-08-02     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2985120R     Medline TA:  J Bacteriol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4615-26     Citation Subset:  IM    
Department of Pediatrics, Children's Hospital and Regional Medical Center, University of Washington, Seattle, WA 98109, USA.
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MeSH Terms
Bacterial Capsules / immunology,  metabolism*
N-Acetylneuraminic Acid / metabolism*
Polysaccharides, Bacterial / metabolism*
Sialyltransferases / metabolism
Streptococcus agalactiae / metabolism*,  pathogenicity
Grant Support
Reg. No./Substance:
0/Bacterial Capsules; 0/Polysaccharides, Bacterial; 131-48-6/N-Acetylneuraminic Acid; EC 2.4.99.-/Sialyltransferases

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