O-polysaccharides (OPSs) were obtained by mild acid degradation of the lipopolysaccharides of Escherichia coli O182-O187, and their structures were established by sugar analysis, Smith degradation, and 1H and 13C NMR spectroscopy. In addition to the monosaccharides that occur often in E. coli OPSs (d-Glc, d-Gal, d-Man, d-GlcNAc, d-GalNAc, d-GlcA, l-Fuc, d-Rib), a number of less common components were identified as the OPS constituents, including 2-acetamido-2-deoxy-l-quinovose and 4-deoxy-4-[(S)-3-hydroxybutanoyl-l-alanyl]-d-quinovose (O186), 3-acetamido-3-deoxy-d-fucose (O187), 3-deoxy-3-[(R)-3-hydroxybutanoyl]-d-fucose (O184), and 2,3-diacetamido-2,3-dideoxy-l-rhamnose (O182). The OPS structures of E. coli O183 and O182 are identical to those of the OPS of Shigella boydii type 10 and the capsular polysaccharide of E. coli K48, respectively. The OPSs of E. coli O186 and O123 are closely related differing in the presence of a Glc residue in the former in place of a GlcNAc residue in the latter. The O-antigen gene clusters of the bacteria studied were analyzed and their contents were found to be consistent with the OPS structures. Predicted glycosyltransferases encoded in the gene clusters were tentatively assigned to glycosidic linkages based on similarities to sequences of other E. coli O-serogroups available from GenBank and taking into account the OPS structures established.

Lipopolysaccharide, O-antigen, Escherichia coli, bacterial polysaccharide structure, O-antigen gene cluster

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,3,2	Ac	175.4-176.1	23.1-23.9
3,3,3	Ac	175.4-176.1	23.1-23.9
3,3	bLRhapN3N	100.3	52.6	55.2	71.2	74.9	18.5
3,2	Ac	175.4-176.1	23.1-23.9
3,4,2	Ac	175.4-176.1	23.1-23.9
3,4	bDGlcpN	102.2	57.5	75.0	71.7	77.7	62.3
3	bDGlcpN	102.4	55.5	79.2	76.8	76.5	61.1
	Subst	179.3	70.5	78.1	73.0


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,3,2	Ac	-	2.00-2.05
3,3,3	Ac	-	2.00-2.05
3,3	bLRhapN3N	5.05	4.59	3.95	3.28	3.54	1.34
3,2	Ac	-	2.00-2.05
3,4,2	Ac	-	2.00-2.05
3,4	bDGlcpN	4.46	3.76	3.54	3.47	3.39	3.88-3.88
3	bDGlcpN	4.79	3.67	3.88	3.84	3.44	3.68-3.89
	Subst	-	4.75	4.67	4.46-4.54


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,3,2	Ac		23.1-23.9/2.00-2.05
3,3,3	Ac		23.1-23.9/2.00-2.05
3,3	bLRhapN3N	100.3/5.05	52.6/4.59	55.2/3.95	71.2/3.28	74.9/3.54	18.5/1.34
3,2	Ac		23.1-23.9/2.00-2.05
3,4,2	Ac		23.1-23.9/2.00-2.05
3,4	bDGlcpN	102.2/4.46	57.5/3.76	75.0/3.54	71.7/3.47	77.7/3.39	62.3/3.88-3.88
3	bDGlcpN	102.4/4.79	55.5/3.67	79.2/3.88	76.8/3.84	76.5/3.44	61.1/3.68-3.89
	Subst		70.5/4.75	78.1/4.67	73.0/4.46-4.54

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

752.724 g/mol (C₃₀H₄₈N₄O₁₈)