Glycosyltransferases of Pseudomonas aeruginosa that assemble the O antigens of A band and B band lipopolysaccharide
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abstract
Pseudomonas aeruginosa produces two forms of lipopolysaccharide (LPS) designated A band and B band. The O-polysaccharide region of A band is a conserved D-rhamnan polymer arranged α1—2, α1—3, α1—3, while B band is serotype-specific with differences in the O-antigenic region dividing P. aeruginosa into 20 stereotypes. The B band O-antigen unit of serotype O5 is [—4)-β-D-Man(2NAc3N)A-(1-4)-β-D-Man(2NAc3NAc)A-(1-3)-α-D-Fuc2NAc]. The glycosidic structure of LPS molecules specified by the action of dedicated glycosyltransferases. The wbp clusters of A band and B band (serotype O5) were each found to contain three genes coding for putative glycosyltransferases: wbpX, wbpY, wbpZ, and wbpH, wbpJ, wbpL , respectively. To examine the role of these potential transferases in LPS assembly, chromosomal mutations were generated within all 6 genes. LPS analysis reveals that wbpX, wbpY, and wbpZ mutants express an A—B+ phenotype, while wbpH and wbpJ mutants are A+B—. Interestingly, mutations in wbpL, an Escherichia coli wec A homologue, abrogates both A band and B band LPS synthesis. Based on amino acid homologies, O-polysaccharide structures and LPS phenotypes of transferase mutants, we propose an assembly scheme for these two LPS molecules.
