Nuh (PA0143) is a nucleoside hydrolase of Pseudomonas aeruginosa PAO1 of the inosine-uridine-preferring (IU-NH) family. It cleaves the N-glycosidic bond of ribonucleosides, releasing the free base and ribose, and is required for growth on adenosine as a sole carbon and energy source. It is annotated as a nonspecific ribonucleoside hydrolase and falls in the PANTHER uridine nucleosidase subfamily, so it probably acts on several purine and pyrimidine ribonucleosides, with adenosine the only experimentally established substrate. Expression of nuh is positively controlled by the LasR quorum-sensing regulator, and the Nuh-negative (no growth on adenosine) phenotype has been used as a convenient assay for LasR function. The protein carries a predicted Sec signal peptide, suggesting it is exported from the cytoplasm rather than cytosolic.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005829 cytosol | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: Cytosol propagated from PAINT node PTN000266727 (PTHR12304 inosine-uridine preferring nucleoside hydrolase clade, 140 leaves in 76 taxa)., seeded by the two cytosolic Arabidopsis enzymes. Reason: The gene product carries a predicted Sec signal peptide (SignalP, residues 1-30), so the mature protein is exported from the cytoplasm, probably to the periplasm; cytosol is propagated from the cytosolic plant seeds and does not fit this bacterial member. Flagged rather than removed because the signal peptide is a single computational line and the location has not been shown experimentally. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: COMPARTMENT OR COMPLEX MISMATCH Sources checked: AGI_LocusCode:AT1G05620 · Arabidopsis URH1-like nucleoside hydrolase SUPPORTS SOURCE BUT NOT TARGET The cytosol IBD at this node is seeded only by two cytosolic plant enzymes. Plant nucleoside hydrolases are cytosolic, but the P. aeruginosa protein carries a Sec signal peptide (SignalP 1-30), so it is exported from the cytoplasm, most likely to the periplasm, where bacterial nucleoside scavenging hydrolases act. Cytosol does not transfer to this bacterial member. PANTHER:PTN000266727 · PTN000266727 SUPPORTS SOURCE BUT NOT TARGET Compartment is not conserved across this 76-taxon clade: it contains both cytosolic (plant) and signal-peptide-bearing (bacterial) members, so the cytosol term is not appropriate at the node level for every leaf. Supporting Evidence: file:PSEAE/nuh/nuh-uniprot.txt FT SIGNAL 1..30 |
| GO:0006152 purine nucleoside catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: Purine nucleoside catabolic process from PTN000266727, consistent with purine nucleosidase activity. Reason: Core process. Nuh hydrolyses adenosine (a purine ribonucleoside), and the gene is required for growth on adenosine as sole carbon source; the hydrolysis of purine nucleosides to base plus ribose is purine nucleoside catabolism. Supporting Evidence: PMID:15995202 lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR |
| GO:0006163 purine nucleotide metabolic process | IMP PMID:15995202 Quorum-sensing-negative (lasR) mutants of Pseudomonas aerugi... | MODIFY | Summary: PseudoCAP IMP; nuh is required for growth on adenosine as sole carbon source. Reason: Wrong branch of the ontology. Nuh is a nucleoside hydrolase: it cleaves the N-glycosidic bond of nucleosides (adenosine), not nucleotides. The process is purine nucleoside catabolism (GO:0006152), already asserted by IBA, not purine nucleotide metabolism. Repoint to GO:0006152. Proposed replacements: purine nucleoside catabolic process Supporting Evidence: PMID:15995202 lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR |
| GO:0006218 uridine catabolic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Uridine catabolic process from PTN000266727, seeded by enzymes with uridine nucleosidase activity. Reason: Plausible for a nonspecific ribonucleoside hydrolase (PANTHER subfamily PTHR12304:SF4, uridine nucleosidase; UniProt name "nonspecific ribonucleoside hydrolase"), but not tested for this gene, whose only experimental substrate is adenosine. Kept as a non-core inferred activity. Supporting Evidence: file:PSEAE/nuh/nuh-uniprot.txt PTHR12304:SF4; URIDINE NUCLEOSIDASE file:PSEAE/nuh/nuh-uniprot.txt PF01156; IU_nuc_hydro |
| GO:0008477 purine nucleosidase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Purine nucleosidase activity from PAINT node PTN000266727 (PTHR12304 inosine-uridine preferring nucleoside hydrolase clade, 140 leaves in 76 taxa). nuh is one of five IBD seeds for GO:0008477 through its PseudoCAP IMP row; the other seeds include the Leishmania major nonspecific nucleoside hydrolase (Q4QDN1, IDA GO:0008477 PMID:10409664, same PANTHER subfamily SF4) and two Arabidopsis enzymes. Reason: Core activity. nuh is a seed of this IBD through its own experimental row (expected, not circular), and the node is grounded in an IDA purine nucleosidase of the same PANTHER subfamily (Leishmania Q4QDN1). The adenosine growth phenotype supports purine nucleosidase activity for nuh itself. Supporting Evidence: PMID:15995202 lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR file:PSEAE/nuh/nuh-uniprot.txt PF01156; IU_nuc_hydro |
| GO:0008477 purine nucleosidase activity | IMP PMID:15995202 Quorum-sensing-negative (lasR) mutants of Pseudomonas aerugi... | ACCEPT | Summary: PseudoCAP IMP seed for the IBD at PTN000266727. lasR/Nuh(-) mutants fail to grow on adenosine as sole carbon source because Nuh, the adenosine-degrading nucleoside hydrolase, is lost. Reason: Seed verdict SOUND. The abstract states that Nuh is the nucleoside hydrolase that degrades adenosine; loss of adenosine utilization when Nuh is absent is genetic evidence that Nuh hydrolyses this purine nucleoside, i.e. purine nucleosidase activity. The evidence is a growth phenotype rather than a direct enzyme assay, but it identifies the activity. Supporting Evidence: PMID:15995202 lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR PMID:15995202 five consecutive cycles of 48 h of incubation sufficed to enrich for about 10% of spontaneous mutants with a Nuh(-) phenotype |
| GO:0016799 hydrolase activity, hydrolyzing N-glycosyl compounds | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO hydrolase acting on N-glycosyl compounds, from the IU nucleoside hydrolase domain. Reason: True but entailed by GO:0008477 purine nucleosidase activity, accepted on this gene (is_a descendant). Supporting Evidence: file:PSEAE/nuh/nuh-uniprot.txt PF01156; IU_nuc_hydro |
| GO:0045437 uridine nucleosidase activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Uridine nucleosidase activity from PTN000266727, seeded by enzymes with this IDA activity (including Leishmania Q4QDN1 and yeast URH1). Reason: Plausible for a nonspecific ribonucleoside hydrolase and consistent with the PTHR12304:SF4 uridine nucleosidase subfamily assignment, but not tested for this gene. Kept as a non-core inferred activity alongside the experimentally supported purine nucleosidase activity. Supporting Evidence: file:PSEAE/nuh/nuh-uniprot.txt PTHR12304:SF4; URIDINE NUCLEOSIDASE file:PSEAE/nuh/nuh-uniprot.txt PF01156; IU_nuc_hydro |
| GO:0045437 uridine nucleosidase activity | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA uridine nucleosidase activity. Reason: Same inference as the IBA uridine nucleosidase row; consistent, not experimentally tested for this gene. Supporting Evidence: file:PSEAE/nuh/nuh-uniprot.txt PTHR12304:SF4; URIDINE NUCLEOSIDASE |
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Download this section (compressed HTML)Q: Where does P. aeruginosa Nuh act? Its predicted signal peptide suggests periplasmic localization, unlike the cytosolic plant orthologs from which the cytosol IBA is propagated.
Q: What is the substrate range of Nuh? The only experimentally shown substrate is adenosine, yet it is classed as a nonspecific/uridine nucleoside hydrolase.
Experiment: Assay purified Nuh against inosine, adenosine, uridine and cytidine to determine its substrate preference, and localize a tagged Nuh by cell fractionation to test the predicted periplasmic location.
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