The structure of the antigenic O-polysaccharide (O-PS) of the lipopolysaccharide (LPS) produced by the enterohemorrhagic strain of Escherichia coli O48:H21 (EHEC) has been elucidated. The O-PS obtained by mild acid hydrolysis of the LPS had [α]D +95 (water) and was composed of L-rhamnose (L-Rha), D-galactose (D-Gal), 2-amino-2-deoxy-D-glucose (D-GlcN), 2-amino-2-deoxy-D-galactose (D-GalN), and D-galacturonic acid (D-GalA) (1:1:1:1:1). From the results of methylation analysis, mass spectrometry, 2D NMR, and DOC-PAGE, the O-PS was shown to be a high molecular mass polymer of a repeating pentasaccharide unit having the structure: [structure: see text]. The D-GalpA non-reducing end groups in the O-PS were partially O-acetylated (approximately 30%) at the O-2 and O-3 positions and the degree of acetylation was variable from batch to batch cell production.

polysaccharide, Escherichia coli O48, LPS O-antigen

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,3,4,2	Ac
3,3,4	bDGlcpN	102.3	56.0	74.2	70.4	75.9	61.0
3,3,2	Ac
3,3	bDGalpN	103.7	52.9	71.3	75.2	74.4	61.6
3	aDGalp	99.1	68.1	79.0	69.6	70.9	61.1
	xL1dEry-ol	17.7	67.0	82.7	61.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,3,4,2	Ac
3,3,4	bDGlcpN	4.72	3.75	3.58	3.44	3.44	3.76-3.93
3,3,2	Ac
3,3	bDGalpN	4.63	3.86	3.86	4.10	3.67	3.78
3	aDGalp	5.10	3.87	3.97	4.16	4.13	3.72
	xL1dEry-ol	1.24	4.05	3.65	3.78-3.80


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,3,4,2	Ac
3,3,4	bDGlcpN	102.3/4.72	56.0/3.75	74.2/3.58	70.4/3.44	75.9/3.44	61.0/3.76-3.93
3,3,2	Ac
3,3	bDGalpN	103.7/4.63	52.9/3.86	71.3/3.86	75.2/4.10	74.4/3.67	61.6/3.78
3	aDGalp	99.1/5.10	68.1/3.87	79.0/3.97	69.6/4.16	70.9/4.13	61.1/3.72
	xL1dEry-ol	17.7/1.24	67.0/4.05	82.7/3.65	61.6/3.78-3.80

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

674.65 g/mol (C₂₆H₄₆N₂O₁₈)