We have analyzed the O-antigen polysaccharide of the previously uncharacterized Escherichia coli strain TD2158 which is a host of bacteriophage HK620. This bacteriophage recognizes and cleaves the polysaccharide with its tailspike protein (TSP). The polysaccharide preparation as well as oligosaccharides obtained from HK620TSP endoglycosidase digests were analyzed with NMR spectroscopy. Additionally, sugar analysis was performed on the O-antigen polysaccharide and MALDI-TOF MS was used in oligosaccharide analysis. The present study revealed a heterogeneous polysaccharide with a hexasaccharide repeating unit of the following structure: [Formula: see text]. A repeating unit with a D-GlcNAc substitution of D-Gal has been described earlier as characteristic for serogroup O18A1. Accordingly, we termed repeating units with D-Glc substitution at D-Gal as O18A2. NMR analyses of the polysaccharide confirmed that O18A1- and O18A2-type repeats were present in a 1:1 ratio. However, HK620TSP preferentially bound the D-GlcNAc-substituted O18A1-type repeating units in its high affinity binding pocket with a dissociation constant of 140 μM and disfavored the O18A2-type having a β-D-Glcp-(1→3)-linked group. As a result, in hexasaccharide preparations, O18A1 and O18A2 repeats were present in a 9:1 ratio stressing the clear preference of O18A1-type repeats to be cleaved by HK620TSP.

Lipopolysaccharide, NMR, Escherichia coli, mass spectrometry, endoglycosidase, Tailspike

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,4,6	aLRhap	98.77	76.74	70.39	73.05	69.77	17.85
3,4	aDGlcp	99.87	72.77	73.68	69.90	71.11	67.36
3,3,2	Ac	175.27	23.17
3,3	bDGlcpN	104.34	56.71	75.05	71.36	76.63	61.91
3	aDGalp	99.99	68.91	79.45	76.85	72.60	60.59
2	Ac	174.85	23.07
6	aDGlcp	98.88	72.40	73.98	70.55	72.77	61.50
	aDGlcpN	96.78	52.67	78.04	71.48	71.36	66.37


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,4,6	aLRhap	4.83	4.03	3.93	3.53	3.78	1.34
3,4	aDGlcp	4.95	3.52	3.72	3.56	4.30	3.92-3.96
3,3,2	Ac	-	2.03
3,3	bDGlcpN	4.66	3.62	3.58	3.41	3.45	3.74-3.95
3	aDGalp	5.47	3.98	3.85	4.30	3.99	3.83-3.83
2	Ac	-	2.09
6	aDGlcp	4.982	3.57	3.78	3.44	3.73	3.77-3.86
	aDGlcpN	5.03	4.14	4.00	3.89	4.25	3.76-4.0


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,4,6	aLRhap	98.77/4.83	76.74/4.03	70.39/3.93	73.05/3.53	69.77/3.78	17.85/1.34
3,4	aDGlcp	99.87/4.95	72.77/3.52	73.68/3.72	69.90/3.56	71.11/4.30	67.36/3.92-3.96
3,3,2	Ac		23.17/2.03
3,3	bDGlcpN	104.34/4.66	56.71/3.62	75.05/3.58	71.36/3.41	76.63/3.45	61.91/3.74-3.95
3	aDGalp	99.99/5.47	68.91/3.98	79.45/3.85	76.85/4.30	72.60/3.99	60.59/3.83-3.83
2	Ac		23.07/2.09
6	aDGlcp	98.88/4.982	72.40/3.57	73.98/3.78	70.55/3.44	72.77/3.73	61.50/3.77-3.86
	aDGlcpN	96.78/5.03	52.67/4.14	78.04/4.00	71.48/3.89	71.36/4.25	66.37/3.76-4.0

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

1038.953 g/mol (C₄₀H₆₆R₂N₂O₂₉, R = next and previous repeats, not counted in mol weight)