The foodborne bacterial pathogen, Campylobacter jejuni, possesses an N-linked protein glycosylation (pgl) pathway involved in adding conserved heptasaccharides to asparagine-containing motifs of >60 proteins, and releasing the same glycan into its periplasm as free oligosaccharides. In this study, comparative genomics of all 30 fully sequenced Campylobacter taxa revealed conserved pgl gene clusters in all but one species. Structural, phylogenetic and immunological studies showed that the N-glycosylation systems can be divided into two major groups. Group I includes all thermotolerant taxa, capable of growth at the higher body temperatures of birds, and produce the C. jejuni-like glycans. Within group I, the niche-adapted C. lari subgroup contain the smallest genomes among the epsilonproteobacteria, and are unable to glucosylate their pgl pathway glycans potentially reminiscent of the glucosyltransferase regression observed in the O-glycosylation system of Neisseria species. The nonthermotolerant Campylobacters, which inhabit a variety of hosts and niches, comprise group II and produce an unexpected diversity of N-glycan structures varying in length and composition. This includes the human gut commensal, C. hominis, which produces at least four different N-glycan structures, akin to the surface carbohydrate diversity observed in the well-studied commensal, Bacteroides. Both group I and II glycans are immunogenic and cell surface exposed, making these structures attractive targets for vaccine design and diagnostics.

Campylobacter jejuni, gene cluster, N-glycosylation

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,4,4,3,2	Ac
3,4,4,3	bDGlcpN	102.5	57.0	74.6	71.1	77.0	61.8
3,4,4,2	Ac
3,4,4,6,2	Ac
3,4,4,6	aDGlcpN	98.1	54.9	72.3	71.2	73.1	61.7
3,4,4	aDGlcpN	99.4	54.2	80.0	69.3	71.9	65.8
3,4,2	Ac
3,4	aDGalpN	99.4	51.4	67.7	77.6	72.3	60.5
3,2	Ac
3	aDGalpN	98.0	50.7	68.0	77.5	72.6	60.9
2	Ac
4	Ac
	bDQuipN4N	95.6	57.2	75.9	58.3	72.3	17.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,4,4,3,2	Ac
3,4,4,3	bDGlcpN	4.58	3.70	3.59	3.48	3.48	3.77-3.93
3,4,4,2	Ac
3,4,4,6,2	Ac
3,4,4,6	aDGlcpN	4.93	3.92	3.78	3.50	3.75	3.79-3.85
3,4,4	aDGlcpN	4.90	4.05	3.95	3.76	4.33	3.57-4.01
3,4,2	Ac
3,4	aDGalpN	5.02	4.28	4.14	4.08	4.37	3.59-3.64
3,2	Ac
3	aDGalpN	5.21	4.23	3.83	4.05	3.89	3.70-3.75
2	Ac
4	Ac
	bDQuipN4N	4.73	3.78	3.81	3.80	3.54	1.17


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,4,4,3,2	Ac
3,4,4,3	bDGlcpN	102.5/4.58	57.0/3.70	74.6/3.59	71.1/3.48	77.0/3.48	61.8/3.77-3.93
3,4,4,2	Ac
3,4,4,6,2	Ac
3,4,4,6	aDGlcpN	98.1/4.93	54.9/3.92	72.3/3.78	71.2/3.50	73.1/3.75	61.7/3.79-3.85
3,4,4	aDGlcpN	99.4/4.90	54.2/4.05	80.0/3.95	69.3/3.76	71.9/4.33	65.8/3.57-4.01
3,4,2	Ac
3,4	aDGalpN	99.4/5.02	51.4/4.28	67.7/4.14	77.6/4.08	72.3/4.37	60.5/3.59-3.64
3,2	Ac
3	aDGalpN	98.0/5.21	50.7/4.23	68.0/3.83	77.5/4.05	72.6/3.89	60.9/3.70-3.75
2	Ac
4	Ac
	bDQuipN4N	95.6/4.73	57.2/3.78	75.9/3.81	58.3/3.80	72.3/3.54	17.6/1.17

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CC(=O)N[C@H]1[C@H](O[C@H]2O[C@H](CO)[C@H](O[C@H]3O[C@H](CO)[C@H](O[C@H]4O[C@H](CO[C@H]5O[C@H](CO)[C@@H](O)[C@H](O)[C@H]5NC(C)=O)[C@@H](O)[C@H](O[C@@H]5O[C@H](CO)[C@@H](O)[C@H](O)[C@H]5NC(C)=O)[C@H]4NC(C)=O)[C@H](O)[C@H]3NC(C)=O)[C@H](O)[C@H]2NC(C)=O)[C@@H](NC(C)=O)[C@H](O)O[C@@H]1C

1262.233 g/mol (C₅₀H₈₃N₇O₃₀)