TrpG (PA0649) is the glutamine amidotransferase subunit of the tryptophan-pathway anthranilate synthase of Pseudomonas aeruginosa PAO1. With the large subunit TrpE it forms a heterotetramer in which TrpG hydrolyses L-glutamine and passes the ammonia to TrpE, which converts chorismate to anthranilate, the first committed step of L-tryptophan biosynthesis. trpEG mutants are tryptophan auxotrophs; TrpEG is expressed mainly at low cell density, whereas the paralogous PhnAB anthranilate synthase supplies anthranilate for the quinolone signal PQS at high density. Pseudomonas TrpE and TrpG are phylogenetically closer to the E. coli aminodeoxychorismate synthase subunits PabB and PabA than to E. coli TrpE and TrpG, and since PAO1 lacks a separate pabA, TrpG may also serve folate precursor synthesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000162 L-tryptophan biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: L-tryptophan biosynthetic process from PAINT node PTN000230074 (anthranilate synthase component II clade, 149 leaves in 93 taxa). TrpG is one of eight IBD seeds through its PseudoCAP IMP row; the other seeds include E. coli TrpGD (IDA), B. subtilis TrpG/PabA (IMP), yeast TRP3, S. pombe trp3 and plant ASB subunits. Reason: Core process. trpEG mutants are tryptophan auxotrophs, and the node is well grounded in several independently characterized anthranilate synthase small subunits. The target in its own WITH/FROM reflects its own experimental row, which is expected. Supporting Evidence: PMID:23449919 trpEG mutants are tryptophan auxotrophs but produce PQS PMID:2153661 One anthranilate synthase enzyme participates in tryptophan synthesis; its genes are designated trpE and trpG. |
| GO:0000162 L-tryptophan biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway mapping (L-tryptophan biosynthesis, step 1/5). Reason: Consistent with the experimental and IBA rows. Supporting Evidence: PMID:23449919 trpEG mutants are tryptophan auxotrophs but produce PQS |
| GO:0000162 L-tryptophan biosynthetic process | IMP PMID:2153661 Identification and characterization of genes for a second an... | ACCEPT | Summary: PseudoCAP IMP seed for the IBD at PTN000230074. Essar et al. inactivated both anthranilate synthase gene pairs and returned them to P. aeruginosa; they assign TrpE-TrpG to tryptophan synthesis and PhnA-PhnB to pyocyanin. Reason: Seed verdict SOUND. The abstract states that both gene pairs were inactivated in the chromosome and that TrpEG is the tryptophan-pathway anthranilate synthase; the trpEG mutant is a tryptophan auxotroph (PMID:23449919), and TrpG supplies the glutamine amidotransferase half of the first committed step. The companion paper PMID:2105306 (not cached) also reports the trpG disruption phenotype. Supporting Evidence: PMID:2153661 They were cloned, sequenced, inactivated in vitro by insertion of an antibiotic resistance gene, and returned to P. aeruginosa, replacing the wild-type gene. PMID:2153661 One anthranilate synthase enzyme participates in tryptophan synthesis; its genes are designated trpE and trpG. PMID:23449919 trpEG mutants are tryptophan auxotrophs but produce PQS |
| GO:0004049 anthranilate synthase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Mapping from the curated EC number and Rhea reaction on the UniProt entry. Reason: Core activity. The complete reaction is carried out by the TrpE-TrpG heterotetramer, TrpG supplying the glutamine amidotransferase half-reaction, so contributes_to would be the more accurate qualifier (as recorded for phnB). Supporting Evidence: file:PSEAE/trpG/trpG-uniprot.txt Reaction=chorismate + L-glutamine = anthranilate + pyruvate + L- file:PSEAE/trpG/trpG-uniprot.txt the glutamine-binding beta subunit (TrpG) of anthranilate synthase (AS) |
| GO:0004049 anthranilate synthase activity | IMP PMID:2153661 Identification and characterization of genes for a second an... | ACCEPT | Summary: PseudoCAP IMP; TrpEG identified as the tryptophan-pathway anthranilate synthase by gene inactivation. Reason: Core molecular function of the TrpEG enzyme to which TrpG contributes the glutaminase subunit. The term is right; the qualifier should be contributes_to (defect recorded, as for phnB). Supporting Evidence: PMID:2153661 One anthranilate synthase enzyme participates in tryptophan synthesis; its genes are designated trpE and trpG. file:PSEAE/trpG/trpG-uniprot.txt the glutamine-binding beta subunit (TrpG) of anthranilate synthase (AS) |
| GO:0008652 amino acid biosynthetic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA amino acid biosynthetic process. Reason: True but entailed by GO:0000162 L-tryptophan biosynthetic process, accepted on this gene (is_a descendant). Supporting Evidence: PMID:23449919 trpEG mutants are tryptophan auxotrophs but produce PQS |
| GO:0009073 aromatic amino acid biosynthetic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA aromatic amino acid family biosynthetic process. Reason: True but entailed by GO:0000162 L-tryptophan biosynthetic process, accepted on this gene (is_a descendant). Supporting Evidence: PMID:23449919 trpEG mutants are tryptophan auxotrophs but produce PQS |
| GO:0046654 tetrahydrofolate biosynthetic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Tetrahydrofolate biosynthetic process from PAINT node PTN000747575, seeded by E. coli PabA (P00903). Reason: Plausible but untested for TrpG. PAO1 has no standalone pabA: the only glutamine amidotransferase subunits of the TrpG/PabA type are TrpG and PhnB, and PabB (PA1758) carries only the chorismate-binding domain, so one of them must supply ammonia for 4-amino-4-deoxychorismate synthesis, as the amphibolic TrpG/PabA of B. subtilis does. Essar et al. note that Pseudomonas TrpG is closer to E. coli PabA than to E. coli TrpG. No experiment shows which subunit serves PabB, so this is kept as a non-core inference. Supporting Evidence: PMID:2153661 Pseudomonas TrpE and TrpG are more closely related to E. coli PabB and PabA than to E. coli TrpE and TrpG |
| GO:0046820 aminodeoxychorismate synthase activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: 4-amino-4-deoxychorismate synthase activity from PAINT node PTN000747575, seeded by E. coli PabA (P00903). Reason: As for the tetrahydrofolate row: TrpG is the likeliest partner of the GATase-less PabB in PAO1 and is related to PabA, but no assay shows TrpG-dependent ADC synthesis. Non-core inference; contributes_to would also suit a subunit of the PabA-PabB complex. Supporting Evidence: PMID:2153661 Pseudomonas TrpE and TrpG are more closely related to E. coli PabB and PabA than to E. coli TrpE and TrpG |
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Download this section (compressed HTML)Q: Which glutamine amidotransferase subunit, TrpG or PhnB, partners the GATase-less PabB (PA1758) in 4-amino-4-deoxychorismate synthesis in P. aeruginosa?
Experiment: Test whether a trpG deletion (in a phnB background) causes p-aminobenzoate auxotrophy on low-ammonium medium, and assay ADC synthase activity of purified PabB with TrpG or PhnB.
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