WbpX (PA5449) is a 460-residue glycosyltransferase family 1 (GT4-type) protein of Pseudomonas aeruginosa PAO1 encoded at the 3' end of the A-band (common polysaccharide antigen) lipopolysaccharide gene cluster. Together with WbpY and WbpZ it assembles the A-band O-polysaccharide, a homopolymer of trisaccharide repeats of alpha1-2, alpha1-3, alpha1-3 linked D-rhamnose. WbpX is proposed to transfer the alpha1-2 linked D-rhamnose residue and to act processively, alternating with WbpY, to extend the polymer. A chromosomal wbpX mutant cannot make A-band LPS while B-band LPS synthesis is unaffected. The donor (presumably GDP-D-rhamnose) and linkage specificity have not been shown by enzyme assay.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009103 lipopolysaccharide biosynthetic process | IMP PMID:9680202 Three rhamnosyltransferases responsible for assembly of the ... | TOO GENERAL | Summary: PseudoCAP row. The wbpX mutant cannot synthesise A-band LPS. Reason: True, but entailed by the accepted GO:0009243 O antigen biosynthetic process (A-band is an O-polysaccharide), which is_a lipopolysaccharide biosynthetic process. Supporting Evidence: PMID:9680202 these mutants are unable to synthesize A-band LPS, while B-band synthesis is unaffected |
| GO:0009243 O antigen biosynthetic process | IDA PMID:9680202 Three rhamnosyltransferases responsible for assembly of the ... | ACCEPT | Summary: PseudoCAP row. WbpX is one of the rhamnosyltransferases that assemble the A-band D-rhamnan O-polysaccharide. Reason: WbpX performs a glycosyl-transfer step in assembling the A-band O-polysaccharide repeat; the mutant lacks A-band LPS. Supporting Evidence: PMID:9680202 The A-band polysaccharide is assembled by the alpha-D-rhamnosyltransferases, WbpX, WbpY and WbpZ. |
| GO:0016757 glycosyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN005302544, seeded by WbpX itself and WbpY (Q9HTB9). The self-seed reflects WbpX's own experimental annotation. Reason: Generic glycosyltransferase activity is as precise as GO allows here: there is no generic D-rhamnosyltransferase term, and the linkage and donor have not been shown biochemically. Supporting Evidence: PMID:9680202 The A-band polysaccharide is assembled by the alpha-D-rhamnosyltransferases, WbpX, WbpY and WbpZ. file:PSEAE/wbpX/wbpX-uniprot.txt Pfam; PF00534; Glycos_transf_1; 1. |
| GO:0016757 glycosyltransferase activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO from the glycosyltransferase family 1 domain (IPR001296). Reason: Consistent with the GT1 domain and the A-band rhamnan assembly role. Supporting Evidence: file:PSEAE/wbpX/wbpX-uniprot.txt InterPro; IPR001296; Glyco_trans_1. |
| GO:0016757 glycosyltransferase activity | IMP PMID:9680202 Three rhamnosyltransferases responsible for assembly of the ... | ACCEPT | Summary: PseudoCAP row and a seed of the PTN005302544 IBD. The paper assigns WbpX as an alpha-D-rhamnosyltransferase on the basis of mutant phenotype and repeat-unit structure; the mutant lacks A-band LPS. Reason: Sound seed for the generic term: a GT1-domain protein whose loss abolishes the rhamnan polymer. The specific linkage assignment is inferred, but the generic term does not depend on it. Supporting Evidence: PMID:9680202 The A-band polysaccharide is assembled by the alpha-D-rhamnosyltransferases, WbpX, WbpY and WbpZ. |
Loading supporting content…
Download this section (compressed HTML)Q: Does WbpX alone form the alpha1-2 linkage with GDP-D-rhamnose, and is it processive as proposed?
Experiment: In vitro assay of purified WbpX with GDP-D-rhamnose and synthetic rhamnan acceptors, with linkage analysis by NMR, to define donor, linkage and processivity.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)