Genome Property Definition Page

NameO5(Ec) antigen biosynthesis
DescriptionThe O5 antigen monomer is a linear tetrasaccharide observed in E. coli strain 97.0246. It consists of the repeating unit [->4)-b-D-Gal-(1->3)-a-D-GalNAc-(1->4)-b-D-Qui3NAc-(1->3)-b-D-Rib-(1->] [1]. Note that the structure reported at ECODAB for O5 actually refers to a different antigen, that from strain 180/C3 [2], which differs in the position of the linkage to the D-Qui3NAc sugar, as well as the reported order of the residues in the monomer unit which are cyclically permuted (this may result in similar antigenic properties while resulting from biosynthetic machinery that is relatively less-well conserved than expected from the overall structural similarity). This alternate structure from 180/C3, for which there is no sequence data, is more similar to the structure of the O114(Ec) antigen which is similarly permuted, and accordingly, the O5 and O114 biosynthetic clusters have only moderate similarity. Qui3NAc is 3-acetamido-3,6-dideoxy-D-glucose, and is likely made from 4,6-dideoxy-4-oxo-dTDP-D-glucose, the product of the RfbA and RfbB enzymes found in the cluster. This would then be converted to the desired product via an aminotransferase and an acetyltransferase, both also found in the cluster. UDP-GalNAc is made from UDP-GlcNAc by the product of the gne gene found in the cluster in a similar fashion to the biosynthesis of the O104 monomer. Ribose and Galactose are both generally bioavailable. The cluster should require three distinct glycosyltransferases, but only two genes with known glycosyltransferase domains are present (the same situation is found in the O114 cluster). Both O5 and O114 contain homologs of the WbuN and WbuO genes, both of unknown function. WbuN is a member of the HAD superfamily which is not known to contain any glycosyltransferases, activities more typically being restricted to hydrolysis reactions. Note that ECODAB includes an assignment of the WbuL gene to the third glycosyltransferase reaction, but that gene has no particular homology support for the assignment, has no homolog in the O5 cluster, and is positioned among the D-Qui3NAcyl biosynthetic genes of the O114 cluster, and is more likely to be the D-Qui3N seryl or D-QuiNSer acetyl-transferase enzyme. If WbuN or WbuO (or both) are responsible for the third glycosyltransfer reaction in O5 and O114, it calls into question the reported difference in the order of the sugars in the monomer since O5 and O114 would have very distinct linkages as the third activity if this were the case.
Parent PropertyGenProp0913: E. coli O-antigen monomer biosynthesis clusters
Literature References
[ 1 ]MacLean LL, Perry MB  Structural characterization of the serotype O:5 O-polysaccharide antigen of the lipopolysaccharide of Escherichia coli O:5.  Biochem Cell Biol. 1997;75(3):199-205.  PMID 9404639
Web ReferencesECODAB:O5

Step NameStep NumRequiredEvidence (Method)Evidence Go Terms
O5(Ec)-associated D-Qui3NAc transferaseGT-1YES2953 (RULE_BASE)
O5(Ec)-associated D-galactose transferaseGT-3YES2956 (RULE_BASE)
source of TDP-Qui3NAcQui3NAcYESGenProp1050 (GENPROP): dTDP-3-acetamido-3,6-dideoxy-D-glucose (D-Qui3NAc) biosynthesis from dTDP-3-amino-3,6-dideoxy-D-glucose (Qui3N)
WbuN-like HAD superfamily enzyme of unknown functionWbuNYES2954 (RULE_BASE)
WbuO-like enzyme of unknown functionWbuOYES2955 (RULE_BASE)
source of UDP-GalNAcgneYES2732 (RULE_BASE)
O5(Ec) antigen transporter (flippase) wzxwzx5YES2951 (RULE_BASE)
O5(Ec) antigen polymerase wzywzy5YES2952 (RULE_BASE)

Parent Properties
GenProp0913E. coli O-antigen monomer biosynthesis clusters

Sibling Properties
GenProp0932O104(Ec) antigen biosynthesis
GenProp0947O55(Ec) antigen biosynthesis
GenProp0949O111(Ec) antigen biosynthesis
GenProp0953O103(Ec) antigen biosynthesis
GenProp0963O2(Ec) antigen biosynthesis
GenProp1018O8(Ec) antigen biosynthesis
GenProp1042O128(Ec) antigen biosynthesis