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Proc Natl Acad Sci U S A 2007 Jul 10;104(28):11557-61

Extracellular structure of polysialic acid explored by on cell solution NMR.

Azurmendi HF, Vionnet J, Wrightson L, Trinh LB, Shiloach J, Freedberg DI


The capsular polysaccharide of the pathogens Neisseria meningitidis serogroup B and of Escherichia coli K1, alpha(2 --> 8) polysialic acid (PSA), is unusual, because when injected into adult humans, it generates little or no antibody. In contrast, people infected with these pathogens generate specific serum antibodies. A structural study on cells is used to address this anomaly by characterizing antigen structures in vivo. We introduce on cell multidimensional solution NMR spectroscopy for direct observation of PSA on E. coli bacteria. Using (13)C,(15)N-labeled PSA, we applied a combination of heteronuclear NMR methods, such as heteronuclear single quantum coherence, HNCA, and HNCO, in vivo. Analysis reveals that free and cell-bound PSA are structurally similar, indicating that the poor immunogenicity of PSA is not due to major structural differences between cells and purified PSA. The (13)C linewidths of PSA on cells are 2 to 3 times larger than the corresponding ones in free PSA. The possible implications of the differences between free and on cell PSA are discussed. In addition, we demonstrate the suitability of the method for in vivo kinetic studies.

Category: Journal Article
PubMed ID: #17609375
Includes FDA Authors from Scientific Area(s): Biologics
Entry Created: 2011-10-04 Entry Last Modified: 2012-08-29