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Characterization of cpsF and its product CMP-N-acetylneuraminic acid synthetase, a group B streptococcal enzyme that can function in K1 capsular polysaccharide biosynthesis in Escherichia coli.
- Source :
- Molecular Microbiology; Feb1996, Vol. 19 Issue 3, p555-563, 9p, 3 Diagrams, 2 Charts
- Publication Year :
- 1996
-
Abstract
- Group B <em>Streptococcus</em> (GBS) is the foremost cause of neonatal sepsis and meningitis in the United States. A major virulence factor for GBS is its capsular polysaccharide, a high molecular weight polymer of branched oligosaccharide subunits. <em>N</em>-acetylneuraminic acid (Neu5Ac or sialic acid), at the end of the polysaccharide side chains, is critical to the virulence function of the capsular polysaccharide. Neu5Ac must be activated by CMP-Neu5Ac synthetase before it is incorporated into the polymer. We showed previously that a transposon mutant of a serotype III GBS strain which had no detectable capsular Neu5Ac was deficient in CMP-Neu5Ac-synthetase activity (Wessels <em>et al.</em>, 1992). In this paper, we report the identification and characterization of <em>cpsF</em>, a gene interrupted by transposon insertion in the previously described Neu5Ac-deficient mutant. The predicted amino acid sequence of the <em>cpsF</em> gene product shares 57% similarity and 37% identity with CMP-Neu5Ac synthetase encoded by the <em>Escherichia coli</em> K1 gene, <em>neuA</em>. The enzymatic function of the protein encoded by <em>cpsF</em> was established by cloning the gene in <em>E. coli</em> under the control of the T7 polymerase/promoter. Lysates of <em>E. coli</em> in which the <em>cpsF</em> gene product was expressed, catalysed the condensation of CTP with Neu5Ac to form CMP-Neu5Ac. In addition, when a CMP-Neu5Ac synthetase-deficient mutant of <em>E. coli</em> K1 was transformed with <em>cpsF</em>, K1 antigen expression was restored. We conclude that <em>cpsF</em> encodes CMP-Neu5Ac synthetase in type III GBS, and that the GBS enzyme can function in the capsule-synthesis of a heterologous bacterial species. [ABSTRACT FROM AUTHOR]
- Subjects :
- SIALIC acids
STREPTOCOCCUS
POLYSACCHARIDE synthesis
BIOSYNTHESIS
AMINO acids
PROTEINS
Subjects
Details
- Language :
- English
- ISSN :
- 0950382X
- Volume :
- 19
- Issue :
- 3
- Database :
- Complementary Index
- Journal :
- Molecular Microbiology
- Publication Type :
- Academic Journal
- Accession number :
- 21322668
- Full Text :
- https://doi.org/10.1046/j.1365-2958.1996.395931.x