PA1342 (AatJ) is the periplasmic solute-binding protein of the AatJQMP (PA1342-PA1339) ABC importer for acidic amino acids in Pseudomonas aeruginosa, orthologous to AatJ of Pseudomonas putida and GltI of Escherichia coli. It is a 302-residue SBP_bac_3 family protein with an N-terminal signal peptide. The purified protein binds L-glutamate (Kd about 1.4 uM) and L-aspartate (about 20 uM) and not other amino acids, and delivers them to the PA1341/PA1340 permeases for ATP-driven uptake across the inner membrane. The transporter is induced by D-glutamate and is needed for growth on D-glutamate.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006865 amino acid transport | IBA GO_REF:0000033 | MODIFY | Summary: Correct for this SBP_bac_3 amino acid binding protein clade; for PA1342 the substrates (L-Glu, L-Asp) and the direction (import) are known. Reason: The node term suits a clade of periplasmic amino acid binding proteins of varied specificity and is grounded by E. coli GltI (IDA L-glutamate transmembrane transport). Q9I402 in its own WITH/FROM marks its PseudoCAP seed, which is expected. PA1342 binds only L-Glu and L-Asp (ITC) and is the binding protein of an ABC importer, so the specific processes are L-glutamate and L-aspartate import across the plasma membrane, as already chosen for the PA1340 and PA1341 permeases of the same transporter. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: UniProtKB:P37902 · E. coli GltI SUPPORTS TRANSFER EcoCyc IDA for L-glutamate transmembrane transport and IPI for glutamate and aspartate binding; grounds the node on its own. UniProtKB:Q9I402 · PA1342 (self; PseudoCAP IMP PMID:25082951) SUPPORTS TRANSFER Abstract states the AatJMQP transporter is essential for D-Glu use; supports the general term. PANTHER:PTN004739212 · PTN004739212 SUPPORTS TRANSFER SBP_bac_3 amino acid binding protein clade (GltI, GlnH and relatives). Proposed replacements: L-glutamate import across plasma membrane L-aspartate import across plasma membrane Supporting Evidence: PMID:31627455 ITC studies revealed l-Glu and l-Asp binding with affinities of 1.4 and 20 µM, respectively. No binding was observed for other amino acids, including l-Gln and l-Asn, indicating that PA1342 is specific for l-Glu and l-Asp (Table 1). PMID:18310026 We describe an ATP-binding cassette (ABC) transporter in Pseudomonas putida KT2440 that mediates the uptake of glutamate and aspartate. |
| GO:0030288 outer membrane-bounded periplasmic space | IBA GO_REF:0000033 | ACCEPT | Summary: Periplasmic binding protein with a cleavable signal peptide. Reason: Seeded by E. coli GltI (periplasm by IDA); PA1342 has a predicted signal peptide and the SBP_bac_3 fold of periplasmic binding proteins. This is where substrate capture takes place. Supporting Evidence: file:PSEAE/PA1342/PA1342-uniprot.txt SIGNAL 1..23 /evidence="ECO:0000255" |
| GO:0042597 periplasmic space | IEA GO_REF:0000044 | TOO GENERAL | Summary: True but entailed by the accepted outer membrane-bounded periplasmic space. Reason: Outer membrane-bounded periplasmic space (GO:0030288), accepted on the IBA row, is an is_a child of this term. |
| GO:0042940 D-amino acid transport | IMP PMID:25082951 Functional characterization of the dguRABC locus for D-Glu a... | KEEP AS NON CORE | Summary: He et al. 2014 report that the AatJMQP transporter is induced by D-Glu and essential for D-Glu utilisation in PAO1. Reason: Abstract only; which aat gene was mutated is not stated, so I defer to the curator who read the full text. D-glutamate is a secondary, condition-specific substrate of the system, and purified PA1342 is reported to bind L-Glu and L-Asp specifically, with no D-Glu binding reported (PMID:31627455), so how the binding protein contributes to D-Glu uptake is open. GO has no D-glutamate transport term, so D-amino acid transport is as precise as GO allows; kept as non-core, matching the same row on PA1340. Supporting Evidence: PMID:25082951 expression of the previously characterized AatJMQP transporter for acidic l-amino acid uptake was found inducible by D-Glu and essential for D-Glu utilization |
| GO:0016595 glutamate binding | IDA PMID:31627455 Determination of Ligand Profiles for Pseudomonas aeruginosa ... | NEW | Summary: Purified PA1342 binds L-glutamate (ITC Kd 1.4 uM). Reason: Direct binding by thermal shift and ITC on the purified P. aeruginosa protein; this is the substrate-capture activity of the binding protein and the basis of the UniProt function statement. E. coli GltI carries the same term by IPI. Supporting Evidence: PMID:31627455 Thermal shift assays showed only stabilization in the presence of three ligands, namely l-Glu, l-Asp, and N-phthaloyl-l-glutamic acid (Table 1). ITC studies revealed l-Glu and l-Asp binding with affinities of 1.4 and 20 µM, respectively. |
| GO:0070335 aspartate binding | IDA PMID:31627455 Determination of Ligand Profiles for Pseudomonas aeruginosa ... | NEW | Summary: Purified PA1342 binds L-aspartate (ITC Kd 20 uM). Reason: Same ITC experiment as the glutamate row; aspartate is the second high-affinity ligand, consistent with the P. putida orthologue. Supporting Evidence: PMID:31627455 indicating that PA1342 is specific for l-Glu and l-Asp (Table 1) |
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Download this section (compressed HTML)Q: Does purified PA1342 bind D-glutamate, and if not, how does the AatJMQP system support growth on D-Glu (for example after periplasmic racemisation, or through DguC handing D-Glu to the Aat permeases)?
Experiment: ITC of purified PA1342 and PA5082 (DguC) with D-glutamate and D-glutamine, and D-[14C]Glu uptake in aatJ, dguC and double mutants.
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