The structure of the O-antigen polysaccharide (PS) from the enteroaggregative Escherichia coli strain 396/C-1 has been determined. Sugar and methylation analyses together with (1)H and (13)C NMR spectroscopy were the main methods used. Inter-residue correlations were determined by (1)H,(1)H-NOESY, (1)H,(13)C-heteronuclear multiple-bond correlation and dipole-dipole cross-correlated relaxation experiments. The PS is composed of pentasaccharide repeating units with the following structure: Analysis of NMR data reveals that on average the PS consists of approximately 13 repeating units and indicates that the biological repeating unit contains an N-acetylglucosamine residue at its reducing end. This structure is different to that reported for the O-antigen polysaccharide from E. coli O126. Monospecific anti-E. coli O126 rabbit serum from The International Escherichia and Klebsiella Centre did not distinguish between the E. coli strain 396/C-1 and the E. coli O126 reference strain, neither in slide agglutination nor in an indirect enzyme immunoassay. Subsequent successful serotyping of the E. coli strain 396/C-1 showed it to be E. coli O126:K+:H27.

Lipopolysaccharide, NMR, Escherichia coli, serology, Enteroaggregative

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,3,3	bDManp	103.5	76.5	72.9	68.3	77.4	62.4
3,3,2	aLFucp	100.4	68.8	70.5	72.7	67.4	16.2
3,3	bDGalp	100.9	75.9	84.0	70.4	75.5	61.7
3,2	Ac	174.2	22.9
3	aDGlcpN	98.0	53.9	76.0	69.0	72.9	61.0
2	Ac	175.2	23.5
	bDGlcpN	100.9	55.1	79.3	72.1	76.8	61.3


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,3,3	bDManp	4.90	4.37	3.58	3.44	3.36	3.64-3.93
3,3,2	aLFucp	5.07	3.77	3.64	3.73	4.25	1.22
3,3	bDGalp	4.68	3.71	3.92	4.18	3.75	3.76
3,2	Ac	-	2.07
3	aDGlcpN	5.33	3.91	4.06	3.57	3.71	3.85
2	Ac	-	2.07
	bDGlcpN	5.01	3.81	3.71	3.65	3.39	3.79-3.91


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,3,3	bDManp	103.5/4.90	76.5/4.37	72.9/3.58	68.3/3.44	77.4/3.36	62.4/3.64-3.93
3,3,2	aLFucp	100.4/5.07	68.8/3.77	70.5/3.64	72.7/3.73	67.4/4.25	16.2/1.22
3,3	bDGalp	100.9/4.68	75.9/3.71	84.0/3.92	70.4/4.18	75.5/3.75	61.7/3.76
3,2	Ac		22.9/2.07
3	aDGlcpN	98.0/5.33	53.9/3.91	76.0/4.06	69.0/3.57	72.9/3.71	61.0/3.85
2	Ac		23.5/2.07
	bDGlcpN	100.9/5.01	55.1/3.81	79.3/3.71	72.1/3.65	76.8/3.39	61.3/3.79-3.91

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@@H]1[C@H](O[C@H]2[C@@H](O)[C@@H](CO)O[C@@H](O[C@H]3[C@H](O)[C@@H](CO)O[C@H](O[C@H]4[C@H](O)[C@@H](CO)O[C@@H](*)[C@@H]4NC(C)=O)[C@@H]3NC(C)=O)[C@@H]2O[C@@H]2O[C@@H](C)[C@@H](O)[C@@H](O)[C@@H]2O)O[C@H](CO)[C@@H](O)[C@@H]1O

876.812 g/mol (C₃₄H₅₆R₂N₂O₂₄, R = next and previous repeats, not counted in mol weight)