MigA (PA0705) is a GT2-family glycosyltransferase that adds the alpha-1,6-linked L-rhamnose to the outer core oligosaccharide of Pseudomonas aeruginosa lipopolysaccharide. P. aeruginosa makes two core glycoforms: an uncapped form carrying alpha-1,6-L-Rha (made by MigA) and an O-antigen-capped form in which the O antigen is attached through alpha-1,3-L-Rha (made by WapR). A migA mutant makes an uncapped core lacking alpha-1,6-L-Rha and loses reactivity to the outer-core antibody 5C101; overexpression of MigA raises the proportion of uncapped core, so the relative levels of MigA and WapR set the ratio of the two glycoforms. migA is positively regulated by RhlR/RhlI quorum sensing. Core truncation in the mutant secondarily alters motility, surface attachment and biofilm mechanics.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009244 lipopolysaccharide core region biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: True for MigA, which has its own structural mutant evidence. MigA and WapR are the only two seeds of this IBD, and the node also covers O-antigen and colanic acid glycosyltransferases, so the node term is too narrow for the clade (defect recorded on wapR). Reason: MigA adds the alpha-1,6-L-Rha of the uncapped LPS core, so lipopolysaccharide core region biosynthesis is correct for this gene. The node-level problem at PTN000531351 does not affect this leaf; it is recorded once, as a GO_CENTRAL defect on the WapR review (genes/PSEAE/wapR), which has the most direct evidence of the two seeds. Supporting Evidence: PMID:18178733 In contrast, uncapped core OS from the migA mutant lacked alpha-1,6-L-Rha. PMID:18178733 These results provide evidence that WapR is the alpha-1,3-rhamnosyltransferase, while MigA is the alpha-1,6-rhamnosyltransferase. |
| GO:0009244 lipopolysaccharide core region biosynthetic process | IMP PMID:18178733 Functional characterization of MigA and WapR: putative rhamn... | ACCEPT | Summary: PseudoCAP seed row: the migA mutant makes an uncapped core lacking alpha-1,6-L-Rha (NMR, MS) and loses the 5C101 outer-core epitope; complementation restores it. Sound. Reason: The abstract states the structural result outright, and the product of MigA is a core sugar, so this is participation, not an indirect phenotype. Core process of the gene. Supporting Evidence: PMID:18178733 In contrast, uncapped core OS from the migA mutant lacked alpha-1,6-L-Rha. PMID:18178733 The migA mutant produced LPS with a truncated outer core and showed no reactivity to outer core-specific monoclonal antibody (MAb) 5C101. PMID:18178733 These results provide evidence that WapR is the alpha-1,3-rhamnosyltransferase, while MigA is the alpha-1,6-rhamnosyltransferase. |
| GO:0015920 lipopolysaccharide transport | IDA PMID:19589832 Truncation in the core oligosaccharide of lipopolysaccharide... | REMOVE | Summary: The cited study compared motility and surface attachment of migA, migA/wapR and rmlC mutants with truncated core; it does not address LPS transport, and the migA product builds the core rather than moving LPS. Reason: Core rhamnosyltransferases act at the cytoplasmic face of the inner membrane before LPS is exported by MsbA and the Lpt machinery. The abstract reports altered motility and attachment as consequences of LPS truncation. Neither result is LPS transport, and an IDA code on a mutant phenotype study does not fit. Removed with a PseudoCAP defect. Supporting Evidence: PMID:19589832 P. aeruginosa wild-type strain PAO1 and three isogenic mutants with defects in the rmlC, migA and wapR genes and producing truncated core oligosaccharide were investigated in terms of motility, attachment to glass and flagella expression. PMID:19589832 LPS truncations probably alter flagella-mediated motility in P. aeruginosa by modulating cell-surface attachment but not flagella synthesis PMID:18178733 These results provide evidence that WapR is the alpha-1,3-rhamnosyltransferase, while MigA is the alpha-1,6-rhamnosyltransferase. |
| GO:0016757 glycosyltransferase activity | IBA GO_REF:0000033 | MODIFY | Summary: Correct; MigA is a GT2 rhamnosyltransferase. The IBD at PTN000531320 has seven seeds and is sound. The specific supported activity is hexosyltransferase (L-rhamnosyl transfer). Reason: Glycosyltransferase activity is correct but general. L-rhamnose is a 6-deoxyhexose and GO places rhamnosyltransferases under GO:0016758 hexosyltransferase activity; no rhamnosyltransferase term for LPS core exists. The IBD at PTN000531320 rests on seven seeds, including IDA rows for Salmonella RfbV, E. coli WcaA, M. tuberculosis Rv2957 and B. subtilis SunS, and stands without MigA. Propagation Review Root cause: NO FAILURE CORE Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000531320 · PTN000531320 SUPPORTS TRANSFER GT2 clade node (44 leaves, 17 taxa) with seven seeds; the generic term suits a clade of glycosyltransferases with different sugar donors. UniProtKB:Q9I5M1 · migA (PA0705) SUPPORTS TRANSFER PseudoCAP IDA seed (PMID:18178733); term correct, evidence is mutant LPS structure (IMP-like). Proposed replacements: hexosyltransferase activity Supporting Evidence: PMID:18178733 These results provide evidence that WapR is the alpha-1,3-rhamnosyltransferase, while MigA is the alpha-1,6-rhamnosyltransferase. file:PSEAE/migA/migA-uniprot.txt PF00535; Glycos_transf_2; 1. file:PSEAE/migA/migA-uniprot.txt GT2; Glycosyltransferase Family 2. |
| GO:0016757 glycosyltransferase activity | IDA PMID:18178733 Functional characterization of MigA and WapR: putative rhamn... | MODIFY | Summary: PseudoCAP seed row: MigA is the alpha-1,6-rhamnosyltransferase, inferred from the specific loss of that linkage in the mutant. Term sound; refine to hexosyltransferase. Reason: The abstract supports MigA as the alpha-1,6-rhamnosyltransferase through mutant structure analysis; no in vitro transfer assay is described, so the IDA code may be generous, but the activity is well supported. Refined to GO:0016758 hexosyltransferase activity, the most specific applicable GO term. Proposed replacements: hexosyltransferase activity Supporting Evidence: PMID:18178733 These results provide evidence that WapR is the alpha-1,3-rhamnosyltransferase, while MigA is the alpha-1,6-rhamnosyltransferase. PMID:18178733 In contrast, uncapped core OS from the migA mutant lacked alpha-1,6-L-Rha. |
| GO:0044010 single-species biofilm formation | IDA PMID:19717596 Differential lipopolysaccharide core capping leads to quanti... | MARK AS OVER ANNOTATED | Summary: Mutants lacking migA make biofilms with altered mechanics and structure, a downstream consequence of LPS core truncation. Reason: The paper uses defined LPS mutants to study how core capping affects adhesion, cohesion and biofilm architecture. That shows LPS structure influences biofilm properties; the migA product, a core glycosyltransferase, does no step of biofilm formation itself. Not removed because the mutant phenotype is real and the full text was not read. Supporting Evidence: PMID:19717596 Using isogenic migA, wapR, and rmlC mutants with defined LPS characteristics, we observed significant changes in cell mechanical properties among these strains compared to wild-type strain PAO1. PMID:19717596 truncation of core oligosaccharides enhanced both adhesive and cohesive forces by up to 10-fold |
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Download this section (compressed HTML)Q: Does MigA transfer L-Rha from dTDP-L-rhamnose to the core acceptor in vitro, and does it compete with WapR for the same acceptor?
Experiment: Assay purified MigA with dTDP-L-rhamnose and a synthetic or purified truncated-core acceptor, and determine the linkage of the product by NMR.
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