pslC (PA2233) encodes PslC, a predicted soluble glycosyltransferase of the GT-2 family (GT-A fold) encoded by the 15-gene psl operon of Pseudomonas aeruginosa. The operon directs synthesis of Psl, a neutral exopolysaccharide built from a repeating pentasaccharide of D-mannose, D-glucose and L-rhamnose. Psl is a principal biofilm matrix polysaccharide of non-mucoid strains, mediating surface attachment and biofilm structure. In-frame deletion of pslC abolishes Psl production and surface attachment. PslC is thought to transfer one of the repeat-unit sugars from a nucleotide-sugar donor during assembly of the lipid-linked repeat unit, but its donor and acceptor specificities have not been determined.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0044010 single-species biofilm formation | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA from PTN002463206, whose biofilm formation IBD is seeded only by this gene's own PseudoCAP row. The target in its own WITH/FROM is expected. Reason: True of PslC in P. aeruginosa, because Psl is a biofilm matrix polymer and a pslC deletion abolishes Psl and attachment. It is a downstream context of Psl synthesis, not the protein's own activity. The node, however, holds only one other characterised leaf, Salmonella RfbN, whose experimentally curated product is the LPS O-antigen; the other five are uncharacterised GT-2-domain or TagF-like proteins with no experimental annotation. Biofilm formation is not an established function of this clade, so the IBD is not a sound family-level claim (see source defect). Supporting Evidence: PMID:19659934 In this study we have demonstrated that eleven of the fifteen psl genes, pslACDEFGHIJKL, are required for Psl synthesis and solid surface attachment. |
| GO:0016757 glycosyltransferase activity | ISS PMID:21991261 Biosynthesis of the Pseudomonas aeruginosa Extracellular Pol... | ACCEPT | Summary: PseudoCAP ISS, from the structural-homology prediction (Phyre2, murine GalNAc-T1 O08912) in the Franklin et al. review. Reason: PslC is a GT-2 family member (Pfam Glycos_transf_2) and is required for Psl synthesis. Its donor sugar is unknown, so the general glycosyltransferase term is as precise as the evidence allows. The ARBA-derived rhamnosyltransferase name in UniProt is an unvetted prediction and is not used here. Supporting Evidence: PMID:21991261 The remaining soluble GT, PslC, is predicted to belong to the CAZy GT-2 family, which adopt a GT-A fold and catalyze glycosyl transfer by an inverting mechanism file:PSEAE/pslC/pslC-uniprot.txt Pfam; PF00535; Glycos_transf_2; 1. |
| GO:0044010 single-species biofilm formation | IDA PMID:19659934 Genetic and biochemical analyses of the Pseudomonas aerugino... | KEEP AS NON CORE | Summary: PseudoCAP IDA; sole seed of the PTN002463206 biofilm formation IBD (7 leaf IBAs). Byrd et al. deleted each psl gene and measured Psl production and surface attachment. Reason: The claim is true for this gene: the pslC deletion mutant made no Psl and was defective in crystal-violet attachment assays. The evidence is a mutant phenotype, so the code should be IMP, not IDA. Biofilm formation is the downstream outcome of PslC's role in Psl synthesis, so the term is peripheral to its core function. Supporting Evidence: PMID:19659934 The same eleven strains that were deficient in attachment likewise did not produce detectable levels of Psl. PMID:19659934 The ability of these fifteen mutants to attach to a solid surface was first assessed by crystal violet staining (Fig. |
| GO:0000271 polysaccharide biosynthetic process | IMP PMID:19659934 Genetic and biochemical analyses of the Pseudomonas aerugino... | NEW | Summary: Proposed. pslC is one of eleven psl genes required for Psl exopolysaccharide synthesis. Reason: PslC is a predicted glycosyltransferase whose deletion abolishes Psl, so it performs a step of Psl assembly itself (glycosyl transfer), not merely being required for it. GO has no Psl-specific term, and the obsolete extracellular polysaccharide biosynthetic process was replaced by this term. Other polysaccharide-synthesis enzymes in P. aeruginosa carry comparable process terms (Pel and alginate machinery). Supporting Evidence: PMID:19659934 Similar to both the crystal violet staining and immunoblot, the ELISA revealed that eleven psl genes, pslACDEFGHIJKL, are essential for Psl production. PMID:21991261 Based on the predicted structures of PslF, PslH, PslI, and PslC, these enzymes likely participate in the transfer of the precursor sugars from activated nucleotide donors to form the repeating unit of the Psl polysaccharide |
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Download this section (compressed HTML)Q: Which nucleotide sugar donor and which lipid-linked acceptor does PslC use in the Psl repeat-unit pathway?
Q: Should the PTN002463206 biofilm formation IBD be removed, given that the clade contains O-antigen, succinoglycan and flagellin glycosyltransferases?
Experiment: Express PslC and assay transfer from GDP-mannose, UDP-glucose and dTDP-rhamnose onto synthetic undecaprenyl-diphosphate-linked Psl intermediates, with LC-MS of products.
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