Abstract
The type R3 core oligosaccharide predominates in the lipopolysaccharides from enterohemorrhagic Escherichia coli isolates including O157:H7. The R3 core biosynthesis (waa) genetic locus contains two genes, waaD and waaJ, that are predicted to encode glycosyltransferases involved in completion of the outer core. Through determination of the structures of the lipopolysaccharide core in precise mutants and biochemical analyses of enzyme activities, WaaJ was shown to be a UDP-glucose:(galactosyl) lipopolysaccharide alpha-1,2-glucosyltransferase, and WaaD was shown to be a UDP-glucose:(glucosyl)lipopolysaccharide alpha-1,2-glucosyltransferase. The residue added by WaaJ was identified as the ligation site for O polysaccharide, and this was confirmed by determination of the structure of the linkage region in serotype O157 lipopolysaccharide. The initial O157 repeat unit begins with an N-acetylgalactosamine residue in a beta-anomeric configuration, whereas the biological repeat unit for O157 contains alpha-linked N-acetylgalactosamine residues. With the characterization of WaaJ and WaaD, the activities of all of the enzymes encoded by the R3 waa locus are either known or predicted from homology data with a high level of confidence. However, when core oligosaccharide structure is considered, the origin of an additional alpha-1,3-linked N-acetylglucosamine residue in the outer core is unknown. The gene responsible for a nonstoichiometric alpha-1,7-linked N-acetylglucosamine substituent in the heptose (inner core) region was identified on the large virulence plasmids of E. coli O157 and Shigella flexneri serotype 2a. This is the first plasmid-encoded core oligosaccharide biosynthesis enzyme reported in E. coli.
Highlights
Lipopolysaccharide (LPS)1 is an essential component of the outer membrane of Gram-negative bacteria and plays an im
From such analyses it is evident that the R1 core type predominates in E. coli isolates most frequently associated with extraintestinal infections, whereas the R3 core type is detected in most enterohemorrhagic E. coli (EHEC) isolates, including O157:H7
We have characterized the waa genetic locus from E. coli F653 encoding enzymes for R3-type core oligosaccharide (core OS) assembly based on analysis of LPS structure in specific waa mutants and biochemical activities of specific enzymes
Summary
Lipopolysaccharide (LPS) is an essential component of the outer membrane of Gram-negative bacteria and plays an im-. The five E. coli core types can be differentiated by polyclonal and monoclonal antibodies [10, 11] and by PCR tests that are based on unique sequences in the waa gene clusters encoding enzymes involved in core OS biosynthesis [12]. From such analyses it is evident that the R1 core type predominates in E. coli isolates most frequently associated with extraintestinal infections, whereas the R3 core type is detected in most enterohemorrhagic E. coli (EHEC) isolates, including O157:H7. K-12 FϪ 80d supE44 ⌬(lacZYA-argF)U196 endA1 hsdR17(rK-12-mK-12) recA1 gyrA96 thi-1 relA1 E. coli B FϪ hsdSB(rBϪmBϪ) gal dcm ompT (DE3) E. coli EC960264; verotoxigenic negative
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
