Abstract
The O-antigen is an essential component of lipopolysaccharide on the surface of Gram-negative bacteria and plays an important role in its pathogenicity. Composition and structure of the O-antigens of Escherichia coli are highly diverse mainly due to genetic variations in the O-antigen gene cluster. In this work, the chemical structure and the gene cluster of the O-antigen of E. coli O161 were studied. Chemical degradations, sugar analyses, and NMR spectroscopy showed that the O161 antigen possesses a trisaccharide O-repeating unit containing a 5- N-acetyl-7- N-( d-alanyl) derivative of 5,7-diamino-3,5,7,9-tetradeoxy- d- glycero- d- galacto-non-2-ulosonic (legionaminic) acid (Leg5Ac7Ala) and having the following structure: → 8 ) - α -Leg p 5 Ac 7 Ala- ( 2 → 4 ) - β - d -Glc p A- ( 1 → 3 ) - β - d -Glc p NAc- ( 1 → The O-antigen gene cluster of E. coli O161 was sequenced. In addition to the genes encoding sugar transferases, O-repeating unit flippase (Wzx) and O-antigen polymerase (Wzy), the genes involved in the biosynthesis of a legionaminic acid derivative were identified based on database similarities.
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