Genetic and structural analyses of Escherichia coli O107 and O117 O-antigens.
The O-antigen, consisting of many repeats of an oligosaccharide, is an essential component of the lipopolysaccharide on the surface of Gram-negative bacteria. The O-antigen is one of the most variable cell constituents, and different O-antigen forms are almost entirely due to genetic variations in O-antigen gene clusters. In this paper, we present structural and genetic evidence for a close relationship between Escherichia coli O107 and E. coli O117 O antigens. The O-antigen of E. coli O107 has a pentasaccharide repeating unit with the following structure: -->4)-beta-D-GalpNAc-(1-->3)-alpha-L-Rhap-(1-->4)-alpha-D-GlcpNAc-(1-->4)-beta-D-Galp-(1-->3)-alpha-D-GalpNAc-(1-->, which differs from the known repeating unit of E. coli O117 only in the substitution of D-GlcNAc for D-Glc. The O-antigen gene clusters of E. coli O107 and O117 share 98.6% overall DNA identity and contain the same set of genes in the same organization. It is proposed that one cluster was evolved from another via mutations, and the substitution of a few amino acids residues in predicted glycosyltransferases resulted in the functional change of one such protein for transferring different sugars in O107 (D-GlcNAc) and O117 (D-Glc), leading to different O-antigen structures. This is an example of the O-antigen alteration caused by nucleotide mutations, which is less commonly reported for O-antigen variations.
Wang
Quan
Q
TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, China.
Perepelov
Andrei V
AV
Feng
Lu
L
Knirel
Yuriy A
YA
Li
Yang
Y
Wang
Lei
L
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002240:Carbohydrate Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics; D023061:Gene Order; D005798:Genes, Bacterial; D016695:Glycosyltransferases / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D020125:Mutation, Missense; D019081:O Antigens / Q000737:chemistry* / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D019081:O Antigens; D016695:Glycosyltransferases