Phase variation of a β‐1,3 galactosyltransferase involved in generation of the ganglioside GM₁‐like lipo‐oligosaccharide of Campylobacter jejuni

Abstract

Ganglioside mimicry by Campylobacter jejuni lipo‐oligosaccharide (LOS) is thought to be a critical factor in the triggering of the Guillain–Barré and Miller–Fisher syndrome neuropathies after C. jejuni infection. The combination of a completed genome sequence and a ganglioside GM1‐like LOS structure makes C. jejuni NCTC 11168 a useful model strain for the identification and characterization of the genes involved in the biosynthesis of ganglioside‐mimicking LOS. Genome analysis identified a putative LOS biosynthetic cluster and, from this, we describe a putative gene (ORF Cj1139c), which we have termed wlaN, with a significant level of similarity to a number of bacterial glycosyltransferases. Mutation of this gene in C. jejuni NCTC 11168 resulted in a LOS molecule of increased electrophoretic mobility, which also failed to bind cholera toxin. Comparison of LOS structural data from wild type and the mutant strain indicated lack of a terminal β‐1,3‐linked galactose residue in the latter. The wlaN gene product was demonstrated unambiguously as a β‐1,3 galactosyltransferase responsible for converting GM2‐like LOS structures to GM1‐like by in vitro expression. We also show that the presence of an intragenic homopolymeric tract renders the expression of a functional wlaN gene product phase variable, resulting in distinct C. jejuni NCTC 11168 cell populations with alternate GM1 or GM2 ganglioside‐mimicking LOS structures. The distribution of wlaN among a number of C. jejuni strains with known LOS structure was determined and, for C. jejuni NCTC 12500, similar wlaN gene phase variation was shown to occur, so that this strain has the potential to synthesize a GM1‐like LOS structure as well as the ganglioside GM2‐like LOS structure proposed in the literature.

A Single Bifunctional UDP-GlcNAc/Glc 4-Epimerase Supports the Synthesis of Three Cell Surface Glycoconjugates in Campylobacter jejuni

“…The gne (Cj1131c) gene of C. jejuni NCTC 11168 was initially annotated to encode a UDP-glucose 4-epimerase (GalE) based on functional characterization of its product (8,9). New evidence presented in this report conclusively demonstrates that gne encodes a bifunctional UDP-GlcNAc/Glc 4-epimerase.…”

In Vitro Biosynthesis of UDP-N,N‘-Diacetylbacillosamine by Enzymes of the Campylobacter jejuni General Protein Glycosylation System

“…NIH-PA Author Manuscript NIH-PA Author Manuscript (7)(8)(9)(10). The genes coding for enzymes that synthesize these glycan moieties have been found in clusters throughout the C. jejuni genome.…”

“…Pseudaminic acid, the major modification of flagellin, is synthesized via the UDP-GlcNAc dehydratase PseB pathway (30,18). GalNAc, a major component in the biosynthesis of glycoprotein N-linked heptasaccharide, lipooligosaccharide (LOS), and capsule (7,8,10), is synthesized intracellularly by the C4 epimerase Gne (31). Table 3 lists the kinetic parameters of PseB and Gne derived from other studies, as well as GST-PglF from this study.…”

Ganglioside Molecular Mimicry and Its Pathological Roles in Guillain-Barré Syndrome and Related Diseases

“…Clearly, the identification of other genes involved in LOS synthesis and the study of their regulation are of considerable interest for a better understanding of the pathogenic mechanisms used by C. jejuni (24). In this regard, Linton et al (49) have reported that the wlaN gene product, which encodes a ␤-1,3-galactosyltransferase, is responsible for converting the GM2-like LOS structure to a GM1-like structure. The LPS of C. jejuni strain 81-176 expresses mainly a mixture of LPS cores containing GM2 and GM3 gangliosides (29).…”