OpdP (OccD3, PA4501) is an outer membrane channel of the OccD subfamily of the Pseudomonas aeruginosa outer membrane carboxylate channel (Occ, formerly OprD) family, the closest paralog of OprD. It is a beta-barrel with an N-terminal extension that constricts the pore in the crystal structure; reconstituted channels show a large dominant conductance with low-conductance substates. OpdP mediates efficient arginine uptake and also transports glycine-glutamate and other dipeptides, and carbapenems such as imipenem and meropenem can translocate along the same path through its constriction zone. In P. aeruginosa opdP lies in an operon with the dipeptide-binding protein gene dppA4.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0015288 porin activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002160747 (seeds OprD, this gene and OprE). Reason: Sound: the IBD rests on OprD, and OpdP has its own direct channel evidence (single-channel recordings, vesicle arginine uptake). Supporting Evidence: PMID:22272184 Remarkably, the conductance of the dominant state of OccD3 is the largest of all channels analyzed PMID:28440622 single OccD3 channels in a planar lipid bilayer |
| GO:0015288 porin activity | IDA PMID:25338022 High-throughput screening of dipeptide utilization mediated ... | ACCEPT | Summary: PseudoCAP IDA porin activity and this gene's PTN002160747 seed row. Full text of the cited Dpp paper contains no OpdP experiment; it names opdP as the operon partner of dppA4 and cites earlier work for its transport role. Reason: The claim is correct (OccD3 forms channels and mediates arginine uptake), so the row stays consistent with the other porin rows; the reference is wrong and should be re-pointed, recorded as a PseudoCAP defect. Supporting Evidence: PMID:22272184 The efficient arginine uptake mediated by OccD3 is noteworthy since this protein was shown, like OccD1, to mediate arginine uptake in P. aeruginosa in vivo PMID:25338022 The porin OpdP was previously shown to be involved in the transport of dipeptides as well as of single amino acids in PAO1 [24]. |
| GO:0015288 porin activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO porin activity from the OprD family signature. Reason: Consistent with direct channel data. Supporting Evidence: PMID:28440622 single OccD3 channels in a planar lipid bilayer |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: Membrane from InterPro. Reason: Correct but general; OpdP is an outer membrane beta-barrel channel, so cell outer membrane (GO:0009279). Proposed replacements: cell outer membrane Supporting Evidence: PMID:22272184 most of the water-soluble small molecules are thought to be taken up by members of the Outer membrane carboxylic acid channel (Occ) family |
| GO:0055085 transmembrane transport | IEA GO_REF:0000108 | MODIFY | Summary: Transmembrane transport inferred from porin activity. Reason: Correct but general; OccD3 mediates efficient arginine uptake, so basic amino acid transmembrane transport (GO:1990822). Proposed replacements: basic amino acid transmembrane transport Supporting Evidence: PMID:22272184 The efficient arginine uptake mediated by OccD3 is noteworthy since this protein was shown, like OccD1, to mediate arginine uptake in P. aeruginosa in vivo |
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Download this section (compressed HTML)Q: Does OpdP work with DppA4 as a dedicated outer-membrane/periplasmic route for particular dipeptides, given their shared operon?
Experiment: Compare dipeptide utilisation (Biolog PM plates) of opdP, dppA4 and double mutants to test whether OpdP is the outer membrane entry route for DppA4 substrates.
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