Structure and gene cluster of the O-antigen of Escherichia coli O110 containing an amide of D-galacturonic acid with D-allothreonine.

The O-polysaccharide (O-antigen) was isolated by mild acid degradation of the lipopolysaccharide (LPS) of Escherichia coli O110. The following structure of the linear tetrasaccharide O-unit of the O-polysaccharide was established by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy: D-aThr--6-->4)-α-D-GalpA-(1-->4)-α-D-Galp-(1--3)-α-D-Galp-(1-->3)-β-D-GlcpNAc-(--> where aThr indicates allothreonine. The O-antigen gene cluster of E. coli O110 was sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in full agreement with the O-antigen structure.