LolA (PA2614) is the periplasmic outer-membrane lipoprotein carrier of Pseudomonas aeruginosa. It has a Sec signal peptide and the LolA/LolB/LppX fold with a hydrophobic cavity that holds the acyl chains of a mature lipoprotein. In the Lol pathway the inner-membrane ABC transporter LolCDE (PA2986-PA2988) releases outer-membrane-destined lipoproteins to LolA, forming a soluble LolA-lipoprotein complex that crosses the periplasm and hands its cargo to the outer-membrane receptor LolB for insertion. Reconstitution with purified P. aeruginosa Lol proteins showed this LolCDE to LolA to LolB transfer directly, and P. aeruginosa LolA also accepts lipoproteins from E. coli LolCDE. lolA is essential in P. aeruginosa; LolA depletion weakens the cell envelope (greater SDS sensitivity) and reduces virulence in insect and mouse infection models.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0030288 outer membrane-bounded periplasmic space | IBA GO_REF:0000033 | ACCEPT | Summary: IBA periplasm from the E. coli LolA seed (P61316, IDA). Reason: LolA has a cleavable signal peptide and acts as a soluble periplasmic carrier; the P. aeruginosa protein forms a soluble complex with lipoproteins released by LolCDE. Supporting Evidence: file:PSEAE/lolA/lolA-uniprot.txt SIGNAL 1..21 PMID:26621210 we confirmed the in vitro essentiality of two periplasmic proteins, LptH and LolA, responsible for lipopolysaccharide and lipoproteins transport to the outer membrane respectively |
| GO:0042597 periplasmic space | IEA GO_REF:0000120 | TOO GENERAL | Summary: UniRule/InterPro periplasmic space mapping. Reason: True, but entailed by GO:0030288 outer membrane-bounded periplasmic space (is_a descendant), which this review accepts. Supporting Evidence: file:PSEAE/lolA/lolA-uniprot.txt SIGNAL 1..21 |
| GO:0042953 lipoprotein transport | IBA GO_REF:0000033 | ACCEPT | Summary: IBA lipoprotein transport from the E. coli LolA seed (P61316). Reason: LolA carries lipoproteins across the periplasm from LolCDE to LolB, which is lipoprotein transport; the term describes the same step from the transport side and is not an ancestor of GO:0044874 (as judged for PA2988). Supporting Evidence: PMID:17350955 When incubated in the presence of ATP and a LolA homologue, the reconstituted LolCDE homologue released lipoproteins, leading to the formation of a LolA-lipoprotein complex. |
| GO:0042953 lipoprotein transport | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO from the LolA family signature. Reason: Consistent with the IBA and the reconstitution evidence. Supporting Evidence: file:PSEAE/lolA/lolA-uniprot.txt NCBIfam; TIGR00547; lolA; 1. |
| GO:0044874 lipoprotein localization to outer membrane | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002185387 (LolA clade; 2 seeds, 9 leaf IBAs in 9 taxa). Seeds are E. coli LolA (P61316, CACAO IDA, PMID:7628437) and P. aeruginosa LolA itself (PseudoCAP and CACAO IDA, PMID:17350955). Reason: The node term suits a LolA clade and both seeds have direct biochemical evidence; the IBD would stand on the E. coli seed alone. LolA among its own sources reflects its own IDA. Supporting Evidence: PMID:17350955 These results indicate that Lol proteins are responsible for the sorting of lipoproteins to the outer membrane of P. aeruginosa |
| GO:0044874 lipoprotein localization to outer membrane | IDA PMID:17350955 Characterization of the Pseudomonas aeruginosa Lol system as... | ACCEPT | Summary: PseudoCAP and CACAO IDA (two GOA rows, same paper), the PTN002185387 seed. In the reconstituted system P. aeruginosa LolA accepted lipoproteins from LolCDE and LolB then incorporated them into the outer membrane. Reason: Direct biochemical evidence with purified P. aeruginosa LolA (abstract). Seed verdict SOUND, consistent with the PA2988/PA2986 reviews of the same paper. Supporting Evidence: PMID:17350955 When incubated in the presence of ATP and a LolA homologue, the reconstituted LolCDE homologue released lipoproteins, leading to the formation of a LolA-lipoprotein complex. PMID:17350955 Lipoproteins were then incorporated into the outer membrane depending on a LolB homologue. |
| GO:0044874 lipoprotein localization to outer membrane | IEA GO_REF:0000104 | ACCEPT | Summary: UniRule (HAMAP MF_00240) mapping. Reason: Consistent with the direct evidence. Supporting Evidence: file:PSEAE/lolA/lolA-uniprot.txt HAMAP; MF_00240; LolA; 1. |
| GO:0140598 lipoprotein carrier activity | IDA PMID:17350955 Characterization of the Pseudomonas aeruginosa Lol system as... | NEW | Summary: Proposed molecular function. Purified P. aeruginosa LolA forms a soluble complex with lipoproteins released by LolCDE (P. aeruginosa or E. coli) and delivers them to LolB for outer-membrane insertion, the carrier activity GO:0140598 describes. Reason: The gene has no molecular function annotation. The reconstitution shows LolA binding the lipoprotein and moving it from LolCDE to LolB, which is LolA's own work in the step, not a requirement for it. Supporting Evidence: PMID:17350955 On the other hand, E. coli LolCDE released lipoproteins with this signal and transferred them to LolA of not only E. coli but also P. aeruginosa. |
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Download this section (compressed HTML)Q: How does P. aeruginosa LolA cope with lipoproteins whose sorting signal lies at positions 3 and 4 rather than 2, and does it discriminate them itself or only via LolCDE?
Experiment: In vitro transfer assays with purified P. aeruginosa LolA and lipoproteins carrying position-3/4 variants, released by P. aeruginosa or E. coli LolCDE, to test whether LolA contributes to sorting specificity.
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