Phase variation of a beta-1,3 galactosyltransferase involved in generationof the ganglioside GM(1)-like lipo-oligosaccharide of Campylobacter jejuni

Ganglioside mimicry by Campylobacter jejuni lipooligosaccharide (LOS) is th ought to be a critical factor in the triggering of the Guillain-Barre and M iller-Fisher syndrome neuropathies after C. jejuni infection. The combinati on of a completed genome sequence and a ganglioside GM(1)-like LOS structur e makes C. jejuni NCTC 11168 a useful model strain for the identification a nd characterization of the genes involved in the biosynthesis of gangliosid e-mimicking LOS, Genome analysis identified a putative LOS biosynthetic clu ster and, from this, we describe a putative gene (ORF Cj1139c), which we ha ve termed wlaN,with a significant level of similarity to a number of bacter ial glycosyltransferases. Mutation of this gene in C. jejuni NCTC 11168 res ulted in a LOS molecule of increased electrophoretic mobility, which also f ailed to bind cholera toxin, Comparison of LOS structural data from wild ty pe and the mutant strain indicated lack of a terminal beta-1,3-linked galac tose residue in the latter. The wlaN gene product was demonstrated unambigu ously as a beta-1,3 galactosyltransferase responsible for converting GM(2)- like LOS structures to GM(1)-like by in vitro expression. We also show that the presence of an intragenic homopolymeric tract renders the expression o f a functional wlaN gene product phase variable, resulting in distinct C. j ejuni NCTC 11168 cell populations with alternate GM(1) or GM(2) ganglioside -mimicking LOS structures. The distribution of wlaN among a number of C. je juni strains with known LOS structure was determined and, for C, jejuni NCT C 12500, similar wlaN gene phase variation was shown to occur, so that this strain has the potential to synthesize a GM(1)-like LOS structure as well as the ganglioside GM(2)-like LOS structure proposed in the literature.