PA2988 is one of the two integral inner-membrane permease subunits (LolC/LolE family, ABC-4 integral membrane protein family) of the LolCDE ABC transporter of Pseudomonas aeruginosa, encoded with the LolD ATPase (PA2987) and the second permease PA2986. It has four predicted transmembrane helices flanking a periplasmic MacB-like core domain. The purified P. aeruginosa LolCDE complex, reconstituted into proteoliposomes, releases outer-membrane-specific lipoproteins from the bilayer in an ATP- and LolA-dependent manner, forming the LolA-lipoprotein complex that delivers lipoproteins to LolB and the outer membrane. P. aeruginosa LolCDE does not release lipoproteins carrying the Lys3-Ser4 inner-membrane retention signal, so it sets the sorting specificity of lipoproteins in this organism.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasmic (inner) membrane location from the UniProt subcellular-location mapping. Reason: PA2988 has four Phobius transmembrane helices and is a subunit of LolCDE, which was purified from membranes and reconstituted into proteoliposomes. The LolCDE complex acts in the inner membrane, where it releases lipoproteins to LolA. Supporting Evidence: file:PSEAE/PA2988/PA2988-uniprot.txt TRANSMEM 21..48 PMID:17350955 The LolCDE homologue thus purified was reconstituted into proteoliposomes with lipoproteins. |
| GO:0016020 membrane | IEA GO_REF:0000120 | MODIFY | Summary: Generic membrane location from combined InterPro/ARBA mapping. Reason: Correct but general. The specific location is the cytoplasmic (plasma) membrane, which the gene already carries (GO:0005886). Proposed replacements: plasma membrane Supporting Evidence: file:PSEAE/PA2988/PA2988-uniprot.txt TRANSMEM 21..48 |
| GO:0042953 lipoprotein transport | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO lipoprotein transport from the LolC/E transmembrane family signature. Reason: LolCDE moves lipoproteins out of the inner membrane to LolA, which is directed lipoprotein transport. The term is not a parent of GO:0044874 (lipoprotein localization to outer membrane) but describes the same step from the transport side, and the family signature (TIGR02212 lolCE) fits. Supporting Evidence: file:PSEAE/PA2988/PA2988-uniprot.txt NCBIfam; TIGR02212; lolCE 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:0044874 lipoprotein localization to outer membrane | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002524722 (LolC/LolE clade, 4 seeds, 46 leaf IBAs). Seeds are E. coli LolC (P0ADC3) and LolE (P75958), each with IDA for this term, and PA2988 and PA2986 (IDA, PMID:17350955). Reason: The node term suits a clade of LolC/LolE permeases, and PA2988 has its own reconstitution evidence. The IBD would stand on the E. coli seeds alone. 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. The purified P. aeruginosa LolCDE complex released lipoproteins to LolA in an ATP-dependent reconstitution assay, and LolB then incorporated them into outer membranes. Reason: Direct biochemical evidence on the complex that contains PA2988. This is the PTN002524722 seed row; verdict SOUND. 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:0098797 plasma membrane protein complex | IBA GO_REF:0000033 | MODIFY | Summary: IBA plasma membrane protein complex from the E. coli LolC/LolE seeds. Reason: True but general. LolCDE is an ABC transporter complex; GO:0043190 ATP-binding cassette (ABC) transporter complex is a descendant of GO:0098797, and E. coli LolC and LolE carry it (IPI). PA2988 was purified as part of the P. aeruginosa LolCDE homologue. Propagation Review Root cause: NO FAILURE CORE Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN002524722 · PTN002524722 SUPPORTS TRANSFER LolC/LolE clade node; the complex term is sound for every member. The more specific ABC transporter complex term would also suit the clade. UniProtKB:P0ADC3 · E. coli LolC SUPPORTS TRANSFER IDA plasma membrane protein complex (PMID:10783239) and IPI ABC transporter complex. UniProtKB:P75958 · E. coli LolE SUPPORTS TRANSFER IDA plasma membrane protein complex (PMID:10783239) and IPI ABC transporter complex. Proposed replacements: ATP-binding cassette (ABC) transporter complex Supporting Evidence: PMID:17350955 The LolCDE homologue thus purified was reconstituted into proteoliposomes with lipoproteins. |
| GO:0140306 lipoprotein releasing activity | IDA PMID:17350955 Characterization of the Pseudomonas aeruginosa Lol system as... | NEW | Summary: Proposed molecular function. The reconstituted P. aeruginosa LolCDE complex, which includes PA2988, releases lipoproteins from the membrane to LolA in an ATP-dependent manner, the activity GO:0140306 describes. E. coli LolC and LolE carry this term by IDA and IMP. Reason: The gene has no molecular function annotation. The release assay was done with the purified complex, so the activity is that of LolCDE as a whole, as for the E. coli subunits. 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. |
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Download this section (compressed HTML)Q: Which of the two P. aeruginosa permeases (PA2988 or PA2986) plays the LolC role (recruiting LolA) and which the LolE role (binding the lipoprotein)? Sequence identity to E. coli LolC and LolE alone may not settle it.
Experiment: Pull-down of LolA with LolCDE complexes lacking either permease periplasmic domain, and photo-crosslinking of a substrate lipoprotein, to assign the LolC-like and LolE-like roles to PA2988 and PA2986.
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