WbpW (PA5452) is a bifunctional phosphomannose isomerase / GDP-mannose pyrophosphorylase (type II PMI family) encoded at the 5' end of the A-band (common polysaccharide antigen) O-antigen gene cluster, next to gmd and rmd. It makes GDP-D-mannose, which Gmd and Rmd convert to GDP-D-rhamnose, the sugar donor for the D-rhamnan of A-band lipopolysaccharide. Its N-terminal nucleotidyltransferase domain converts mannose 1-phosphate and GTP to GDP-mannose, and its C-terminal cupin domain interconverts fructose 6-phosphate and mannose 6-phosphate. wbpW complements E. coli PMI and GMP mutants, and wbpW mutants make little A-band. It is functionally redundant with its paralogue PslB: a pslB wbpW double mutant makes neither A-band LPS nor the Psl exopolysaccharide. A third paralogue, AlgA, serves alginate synthesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000271 polysaccharide biosynthetic process | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO from the bifunctional PMI/GMP family signature. Reason: True but uninformative. O antigen biosynthetic process (GO:0009243), accepted in this review, is a descendant and entails it. Supporting Evidence: PMID:19659934 indicating that A-band LPS synthesis requires the redundant PMI/GMP activity of either PslB or WbpW to generate product. |
| GO:0004475 mannose-1-phosphate guanylyltransferase (GTP) activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000283179 (bifunctional PMI-GMP clade, 30 leaf IBAs in 26 taxa), seeded by E. coli ManC (P24174, EcoCyc IDA) and the paralogue AlgA (P07874, PseudoCAP IDA on purified enzyme). Reason: WbpW sits inside the clade with the full nucleotidyltransferase domain, and complementation of an E. coli GMP mutant supports the activity directly for this gene. The IBD is sound on both seeds. Supporting Evidence: PMID:9781879 This indicates that WbpW, like AlgA, is a bifunctional enzyme that possesses both PMI and GMP activities for the synthesis of GDP-D-Man. |
| GO:0004475 mannose-1-phosphate guanylyltransferase (GTP) activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from the GMPP N-terminal domain and EC 2.7.7.13. Reason: Consistent with family membership and the complementation evidence. Supporting Evidence: file:PSEAE/wbpW/wbpW-uniprot.txt GDP-M1P_Guanylyltransferase PMID:9781879 This indicates that WbpW, like AlgA, is a bifunctional enzyme that possesses both PMI and GMP activities for the synthesis of GDP-D-Man. |
| GO:0004476 mannose-6-phosphate isomerase activity | IEA GO_REF:0000003 | ACCEPT | Summary: EC mapping (5.3.1.8) for the type II PMI C-terminal domain. Reason: WbpW restores capsule synthesis to an E. coli PMI mutant and carries the type II PMI C-terminal domain, like its biochemically characterised paralogue AlgA. Supporting Evidence: PMID:9781879 To confirm the enzymatic activity of WbpW, Escherichia coli PMI and GMP mutants deficient in the K30 capsule were complemented with wbpW, and restoration of K30 capsule production was observed. file:PSEAE/wbpW/wbpW-uniprot.txt Mannose-6-phosphate isomerase type II C-terminal |
| GO:0005976 polysaccharide metabolic process | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO from the type II PMI C-terminal domain. Reason: True but uninformative. O antigen biosynthetic process (GO:0009243), accepted in this review, is a descendant and entails it. Supporting Evidence: PMID:19659934 indicating that A-band LPS synthesis requires the redundant PMI/GMP activity of either PslB or WbpW to generate product. |
| GO:0009103 lipopolysaccharide biosynthetic process | IMP PMID:9781879 Synthesis of the A-band polysaccharide sugar D-rhamnose requ... | ACCEPT | Summary: PseudoCAP IMP from wbpW chromosomal mutants with little A-band LPS. Reason: WbpW makes the GDP-D-mannose that Gmd and Rmd convert to the A-band sugar donor GDP-D-rhamnose, so it performs a step of A-band LPS synthesis. Mutants make very little A-band; residual A-band comes from the redundant paralogue PslB. Same action as for gmd in the same pathway. Supporting Evidence: PMID:9781879 The Rmd mutants do not produce A-band LPS, while the WbpW mutants synthesize very low amounts of A band after 18 h of growth. PMID:19659934 In contrast to the other strains, the pslB wbpW double mutant failed to produce detectable A-band polysaccharide |
| GO:0009243 O antigen biosynthetic process | IDA PMID:19659934 Genetic and biochemical analyses of the Pseudomonas aerugino... | ACCEPT | Summary: PseudoCAP row from Byrd et al. 2009, where a pslB wbpW double mutant makes no A-band polysaccharide. Reason: A-band is an O antigen and WbpW supplies its GDP-D-mannose precursor, so the term is right (as for gmd). The evidence is immunoblot of deletion mutants, a mutant phenotype, so the evidence code should be IMP, not IDA. Supporting Evidence: PMID:19659934 In contrast to the other strains, the pslB wbpW double mutant failed to produce detectable A-band polysaccharide PMID:19659934 indicating that A-band LPS synthesis requires the redundant PMI/GMP activity of either PslB or WbpW to generate product. |
| GO:0009298 GDP-mannose biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000283179, seeded by E. coli ManC (P24174, EcoCyc EXP) and by wbpW itself (PseudoCAP IDA, PMID:9781879). The self-seed is expected, not circular. Reason: Bifunctional PMI-GMP enzymes make GDP-mannose from fructose 6-phosphate (with AlgC phosphomannomutase) or mannose 1-phosphate. The node term suits the clade and the IBD stands on ManC alone. Supporting Evidence: PMID:9781879 This indicates that WbpW, like AlgA, is a bifunctional enzyme that possesses both PMI and GMP activities for the synthesis of GDP-D-Man. |
| GO:0009298 GDP-mannose biosynthetic process | IDA PMID:9781879 Synthesis of the A-band polysaccharide sugar D-rhamnose requ... | ACCEPT | Summary: PseudoCAP row, seed of the PTN000283179 GDP-mannose biosynthesis IBD. Seed verdict SOUND (term), with an evidence-code problem. Reason: The abstract shows that wbpW restores K30 capsule synthesis to E. coli PMI and GMP mutants, which supports participation in GDP-mannose synthesis. The abstract describes no assay with WbpW protein, so the evidence is heterologous genetic complementation (IGI) rather than IDA. Supporting Evidence: PMID:9781879 To confirm the enzymatic activity of WbpW, Escherichia coli PMI and GMP mutants deficient in the K30 capsule were complemented with wbpW, and restoration of K30 capsule production was observed. |
| GO:0009298 GDP-mannose biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway mapping (UPA00126, GDP-alpha-D-mannose biosynthesis). Reason: Consistent with the IBA and complementation evidence; same action as for algA and algC. Supporting Evidence: PMID:9781879 This indicates that WbpW, like AlgA, is a bifunctional enzyme that possesses both PMI and GMP activities for the synthesis of GDP-D-Man. |
| GO:0016779 nucleotidyltransferase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO nucleotidyltransferase activity. Reason: True, but mannose-1-phosphate guanylyltransferase (GTP) activity (GO:0004475), accepted here, is a descendant and entails it. Supporting Evidence: file:PSEAE/wbpW/wbpW-uniprot.txt GDP-M1P_Guanylyltransferase |
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Download this section (compressed HTML)Q: Did Rocchetta et al. (PMID:9781879) assay PMI or GMP activity with purified or overexpressed WbpW, or does the GDP-mannose biosynthesis row rest only on E. coli complementation (IGI rather than IDA)?
Experiment: Purify WbpW and measure PMI and GMP kinetics alongside AlgA and PslB, to test whether the three paralogues differ in substrate preference or regulation in a way that explains their pathway-specific roles.
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