Periplasmic MlaC-family phospholipid carrier in the Ttg2/Mla system. Ttg2D binds membrane phospholipids in a hydrophobic pocket and shuttles them between the outer-membrane VacJ/MlaA interface and inner-membrane MlaFEDB.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005543 phospholipid binding | IDA PDB:5UWB | NEW | Summary: Q88P91 is an MlaC-family carrier with target-specific apo and lipid-bound structures. Reason: The solved hydrophobic-pocket architecture directly supports phospholipid binding, while exact loading stoichiometry remains uncertain for KT2440. Supporting Evidence: PDB:5UWB Lipid-bound crystal structure of Q88P91/PP_0961. |
| GO:0030288 outer membrane-bounded periplasmic space | ISS file:PSEPK/ttg2D/ttg2D-deep-research-openscientist.md | NEW | Summary: Ttg2D is the soluble periplasmic carrier between the two membrane interfaces. Reason: MlaC-family identity and its carrier role in the diderm envelope support periplasmic localization. Supporting Evidence: file:PSEPK/ttg2D/ttg2D-deep-research-openscientist.md Consistent with its cleaved Sec signal peptide and the **absence of a lipobox** (i.e., it is not lipid-anchored to a membrane), Ttg2D is a **soluble protein resident in the periplasmic space**. |
| GO:0120010 intermembrane phospholipid transfer | ISS file:PSEPK/ttg2D/ttg2D-deep-research-openscientist.md | NEW | Summary: Ttg2D shuttles phospholipid between the outer- and inner-membrane Mla interfaces. Reason: The MlaC-family assignment and complete local Mla/Ttg2 system support intermembrane transfer without fixing net direction. Supporting Evidence: file:PSEPK/ttg2D/ttg2D-deep-research-openscientist.md Ttg2D is therefore the mobile lipid-carrier module of this shuttle. |
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Download this section (compressed HTML)Q: Which phospholipid classes and acyl-chain compositions are preferred by KT2440 Ttg2D?
Q: What is the net physiological transfer direction of the KT2440 Ttg2/Mla system, and which outer-membrane protein receives or donates lipid to Ttg2D?
Experiment: Measure loading and unloading of purified Ttg2D against VacJ/MlaA and MlaFEDB proteoliposomes with defined lipid mixtures.
Type: phospholipid-transfer and lipidomics assay
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: Binding stoichiometry and phospholipid-class preferences have not been measured directly for Q88P91.
OPEN BIOLOGY
Significance: The target structure establishes lipid binding, whereas quantitative specificity derives from the Pseudomonas aeruginosa ortholog.
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