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Predicted functions and linkage specificities of the products of the Streptococcus pneumoniae capsular biosynthetic loci.

ABSTRACT: The sequences of the capsular biosynthetic (cps) loci of 90 serotypes of Streptococcus pneumoniae have recently been determined. Bioinformatic procedures were used to predict the general functions of 1,973 of the 1,999 gene products and to identify proteins within the same homology group, Pfam family, and CAZy glycosyltransferase family. Correlating cps gene content with the 54 known capsular polysaccharide (CPS) structures provided tentative assignments of the specific functions of the different homology groups of each functional class (regulatory proteins, enzymes for synthesis of CPS constituents, polymerases, flippases, initial sugar transferases, glycosyltransferases [GTs], phosphotransferases, acetyltransferases, and pyruvyltransferases). Assignment of the glycosidic linkages catalyzed by the 342 GTs (92 homology groups) is problematic, but tentative assignments could be made by using this large set of cps loci and CPS structures to correlate the presence of particular GTs with specific glycosidic linkages, by correlating inverting or retaining linkages in CPS repeat units with the inverting or retaining mechanisms of the GTs predicted from their CAZy family membership, and by comparing the CPS structures of serotypes that have very similar cps gene contents. These large-scale comparisons between structure and gene content assigned the linkages catalyzed by 72% of the GTs, and all linkages were assigned in 32 of the serotypes with known repeat unit structures. Clear examples where very similar initial sugar transferases or glycosyltransferases catalyze different linkages in different serotypes were also identified. These assignments should provide a stimulus for biochemical studies to evaluate the reactions that are proposed.

SUBMITTER: Aanensen DM

PROVIDER: S-EPMC2168755 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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Predicted functions and linkage specificities of the products of the Streptococcus pneumoniae capsular biosynthetic loci.

Aanensen David M DM Mavroidi Angeliki A Bentley Stephen D SD Reeves Peter R PR Spratt Brian G BG

Journal of bacteriology 20070831 21

The sequences of the capsular biosynthetic (cps) loci of 90 serotypes of Streptococcus pneumoniae have recently been determined. Bioinformatic procedures were used to predict the general functions of 1,973 of the 1,999 gene products and to identify proteins within the same homology group, Pfam family, and CAZy glycosyltransferase family. Correlating cps gene content with the 54 known capsular polysaccharide (CPS) structures provided tentative assignments of the specific functions of the differen ...[more]

PMID: 17766420

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Project description:Capsular polysaccharides (CPS) are crucial virulence factors of Streptococcus pneumoniae The previously unknown CPS structures of the pneumococcal serogroup 16 (serotypes 16F and 16A) were thoroughly elucidated by nuclear magnetic resonance (NMR) spectroscopy and verified by chemical analysis. The following repeat unit structures were determined: 16F, -3)-α-l-Rhap-[4-P-1-Gro]-(1-3)-α-d-Glcp-[(6-P-1)-Gro]-(1-3)-β-l-Rhap-[2-OAc]-(1-4)-β-d-Glcp-(1-; 16A, -3)-β-d-Galf-[2-OAc (70%)]-(1-3)-α-l-Rhap-(1-2)-α-l-Rhap-(1-3)-α-d-Galp-[(6-P-1)-Gro]-(1-3)-β-d-Galp-(1-4)-β-d-Glcp-(1- (OAc, O-acetyl substitution; P-1-Gro, glycerol-1-phosphate substitution) A further analysis of CPS biosynthesis of serotypes 16F and 16A, in conjunction with published cps gene bioinformatics analysis and structures of related serotypes, revealed presumable specific function of glycosyltransferase, acetyltransferase, phosphotransferase, and polymerase. The functions of glycosyltransferases WcxN and WcxT were proposed for the first time, and they were assigned to catalyze linkage of α-l-Rhap-(1-3)-α-d-Glcp and α-l-Rhap-(1-2)-α-l-Rhap, respectively. Furthermore, since serotype 16F was genetically close to serogroup 28, cross-reactions between serogroup 16 and serogroup 28 were studied using diagnostic antisera, which provided further understanding of antigenic properties of CPS and diagnostic antisera. Interestingly, serotype 16F cross-reacted with factor antisera 28b and 11c. Meanwhile, serotype 16A cross-reacted with factor antiserum 11c.IMPORTANCE The vaccine pressure against Streptococcus pneumoniae could result in a change of prevalence in carriage and invasive serotypes. As such, it is necessary to monitor the distribution to achieve successful vaccination of the population, and similarly, it is important to increase the knowledge of even the currently less prevalent serotypes. The CPS are vital for the virulence of the pathogen, and antigenic properties of CPS are based on the structure. Consequently, a better understanding of the structure, biosynthesis, and serology of the capsular polysaccharides can be of great importance toward developing future diagnostic tools and vaccines.

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Dataset Information

Predicted functions and linkage specificities of the products of the Streptococcus pneumoniae capsular biosynthetic loci.

Publications

Predicted functions and linkage specificities of the products of the Streptococcus pneumoniae capsular biosynthetic loci.

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