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Extended glycan diversity in a bacterial protein glycosylation system linked to allelic polymorphisms and minimal genetic alterations in a glycosyltransferase gene
Author(s) -
Børud Bente,
Asen Jan Haug,
Viburiene Raimonda,
Cohen Ellen Hanne,
Samuelsen Anne Berit C.,
Koomey Michael
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12789
Subject(s) - biology , glycan , glycosylation , gene , glycosyltransferase , genetics , glycobiology , glycomics , glycoprotein , biochemistry , allele , n linked glycosylation
Summary Glycans manifest in conjunction with the broad spectrum O ‐linked protein glycosylation in species within the genus N eisseria display intra‐ and interstrain diversity. Variability in glycan structure and antigenicity are attributable to differences in the content and expression status of glycan synthesis genes. Given the high degree of standing allelic polymorphisms in these genes, the level of glycan diversity may exceed that currently defined. Here, we identify unique protein‐associated disaccharide glycoforms that carry N ‐acetylglucosamine ( GlcNAc ) at their non‐reducing end. This altered structure was correlated with allelic variants of pglH whose product was previously demonstrated to be responsible for the expression of glucose ( Glc )‐containing disaccharides. Allele comparisons and site‐specific mutagenesis showed that the presence of a single residue, alanine at position 303 in place of a glutamine, was sufficient for GlcNAc versus Glc incorporation. Phylogenetic analyses revealed that GlcNAc ‐containing disaccharides may be widely distributed within the pgl systems of N eisseria particularly in strains of N . meningitidis . Although analogous minimal structural alterations in glycosyltransferases have been documented in association with lipopolysaccharide and capsular polysaccharide variability, this appears to be the first example in which such changes have been implicated in glycan diversification within a bacterial protein glycosylation system.