PA1014 (proposed name WapB) is a 330-residue glycosyltransferase of the GT2-like family, with a nucleotide-diphospho-sugar transferase fold, in Pseudomonas aeruginosa PAO1 that acts in biosynthesis of the lipopolysaccharide (LPS) outer core oligosaccharide. A wapB chromosomal mutant makes a core oligosaccharide that lacks the terminal beta-1,2-linked D-glucose residue (Glc IV) and loses reactivity with the outer-core monoclonal antibody 5c-101; complementation restores the wild-type core, and expressing wapB in the 11 IATS serotypes that naturally lack Glc IV adds a terminal glucose to their core. WapB is therefore the glucosyltransferase that adds the terminal beta-1,2-glucose to the LPS outer core. The nucleotide-sugar donor and the transfer reaction have not been shown in vitro.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0008919 lipopolysaccharide glucosyltransferase I activity | IDA PMID:21441506 Evidence that WapB is a 1,2-glucosyltransferase of Pseudomon... | ACCEPT | Summary: PseudoCAP row and a seed of the PTN000531320 glycosyltransferase IBD. GO:0008919 is defined generically (UDP-glucose + lipopolysaccharide = UDP + D-glucosyl-lipopolysaccharide), and WapB adds the terminal beta-1,2-glucose to the LPS outer core. Reason: The mutant structure, complementation and gain-of-function data show that WapB adds a glucose residue to LPS, which is what the GO definition describes. The label's "I" comes from the EC name for the first core glucose (WaaG-type), but the GO definition does not restrict the acceptor position, so the term fits. The UDP-glucose donor is assumed, not shown. The abstract reports only in vivo genetic and structural data, so the IDA code may properly be IMP; this is recorded as a suspected evidence-code defect and does not affect the term. Supporting Evidence: PMID:21441506 revealed that the core OS of the wapB mutant lacked the terminal Ξ²-1,2-linked-d-glucose residue. PMID:21441506 Our results strongly suggested that wapB encodes a 1,2-glucosyltransferase. |
| GO:0009244 lipopolysaccharide core region biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000531351, seeded by the P. aeruginosa outer-core glycosyltransferases WapR (Q9HUG5) and MigA (Q9I5M1). PA1014 is not a seed of this node, but its own mutant data place it in outer-core assembly. Reason: Supported directly for PA1014 by the wapB mutant core structure (loss of the terminal outer-core glucose) and complementation. Supporting Evidence: PMID:21441506 Here, we show that a previously uncharacterized gene, pa1014, is involved in outer core biosynthesis |
| GO:0016757 glycosyltransferase activity | IBA GO_REF:0000033 | TOO GENERAL | Summary: IBA from PTN000531320 (seven seeds, including PA1014 itself, WapR, MigA, B. subtilis SunS, Salmonella RfbV, E. coli WcaA and M. tuberculosis Rv2957). The node term is true for PA1014. Reason: True, but entailed by the accepted GO:0008919 lipopolysaccharide glucosyltransferase I activity, which is_a glycosyltransferase activity. The node-level term suits a 44-leaf GT2 clade of diverse sugar transferases; the IBD stands on the other seeds as well as on PA1014. |
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Download this section (compressed HTML)Q: Is UDP-glucose the donor for WapB, and which outer-core residue is its acceptor in vitro?
Experiment: In vitro glucosyltransferase assay with purified WapB, UDP-glucose and core oligosaccharide from the wapB mutant as acceptor, with product analysis by MS and NMR.
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