The complete genome of Campylobacter jejuni strain RM1221 (Penner serotype HS:53) was reported recently and contains a novel capsular polysaccharide (CPS) biosynthesis locus. Cell-surface carbohydrates such as CPS are known to be important for bacterial survival and often contribute to pathogenesis. In this study, we describe the complete structure of the CPS of C. jejuni RM1221, which was determined by using NMR spectroscopy, MS, and chemical methods. The CPS contains 6-deoxy-D-manno-heptose and D-threo-pent-2-ulose (D-xylulose), two monosaccharides that are rarely found in bacterial polysaccharides. The CPS has a regular structure of a linear main chain of trisaccharide repeating units, composed of two α- and one β-6-deoxy-D-manno-heptopyranose residues, which are linked through a phosphodiester linkage. Branching residues of xylulose are incorporated nonstoichiometrically: each trisaccharide repeating unit of the main chain bears no, one, or two xylulose residues. The xylulose glycosidic linkages are extremely acid labile, and it is not clear how they can be preserved under the acidic conditions of the gastrointestinal tract, where Campylobacter resides during infection. We have also shown that the CPS biosynthesis genes of C. jejuni RM1221 are conserved in other C. jejuni strains of the Penner serotype HS:53, including serotype HS:53 reference strain RM3435

biosynthesis, capsular polysaccharide, Campylobacter jejuni, NMR spectroscopy

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7
3,3,3	P
3,3,2	aDXulf	60.7	?	82.3	77.7	75.4
3,3,4	bDXulf	64.6	109.6	79.8	74.2	70.6
3,3	bD6dmanHepp	97.2	72.4	77.7	71.1	74.3	34.6	59.3
3	aD6dmanHepp
	aD6dmanHepp


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6	H7
3,3,3	P
3,3,2	aDXulf	3.67-3.88	-	4.29	4.29	4.30-4.36
3,3,4	bDXulf	3.53-3.71	-	4.55	4.32	3.79-4.13
3,3	bD6dmanHepp	4.93	4.55	4.22	3.95	3.52	1.78	3.76-3.80
3	aD6dmanHepp
	aD6dmanHepp


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6	C7/H7
3,3,3	P
3,3,2	aDXulf	60.7/3.67-3.88		82.3/4.29	77.7/4.29	75.4/4.30-4.36
3,3,4	bDXulf	64.6/3.53-3.71		79.8/4.55	74.2/4.32	70.6/3.79-4.13
3,3	bD6dmanHepp	97.2/4.93	72.4/4.55	77.7/4.22	71.1/3.95	74.3/3.52	34.6/1.78	59.3/3.76-3.80
3	aD6dmanHepp
	aD6dmanHepp

The spectrum also has 1 signal at unknown position (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*OP(=O)(O)O[C@@H]1[C@H](O[C@@]2(CO)OC[C@@H](O)[C@@H]2O)[C@H](O[C@@H]2[C@H](O)[C@@H](O[C@@H]3[C@H](O)[C@@H](*)O[C@H](CCO)[C@H]3O)O[C@H](CCO)[C@H]2O)O[C@H](CCO)[C@H]1O[C@]1(CO)OC[C@@H](O)[C@@H]1O

872.713 g/mol (C₃₁H₅₃R₂O₂₆P, R = next and previous repeats, not counted in mol weight)