ORPs are lipid-transport proteins belonging to the oxysterol-binding protein family. They facilitate the transfer of lipids between different intracellular membranes, such as the ER and plasma membrane. We have solved the crystal structure of the ORP8 lipid transport domain (ORD8). The ORD8 exhibited a β-barrel fold composed of anti-parallel β-strands, with three α-helices replacing β-strands on one side. This mixed alpha-beta structure was consistent with previously solved structures of ORP2 and ORP3. A large cavity (≈1860 Å3) within the barrel was identified as the lipid-binding site. Although we were not able to obtain a lipid-bound structure, we used computer simulations based on our crystal structure to dock PS and PI4P molecules into the putative lipid-binding site of the ORD8. Comparative experiments between the short ORD8ΔLid (used for crystallography) and the full-length ORD8 (lid containing) revealed the lid's importance for stable lipid binding. Fluorescence assays revealed different transport efficiencies for PS and PI4P, with the lid slowing down transport and stabilizing cargo. Coarse-grained simulations highlighted surface-exposed regions and hydrophobic interactions facilitating lipid bilayer insertion. These findings enhance our comprehension of ORD8, its structure, and lipid transport mechanisms, as well as provide a structural basis for the design of potential inhibitors.

• Klíčová slova
• ER, ORD, ORP8, PI4P, PS, lipid transport, plasma membrane,
• MeSH
• biologický transport MeSH
• buněčná membrána metabolismus   MeSH
• lipidy * chemie   MeSH
• transportní proteiny * metabolismus   MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lipidy * MeSH
• transportní proteiny * MeSH

Phosphatidylinositol (PI) is an essential structural component of eukaryotic membranes that also serves as the common precursor for polyphosphoinositide (PPIn) lipids. Despite the recognized importance of PPIn species for signal transduction and membrane homeostasis, there is still a limited understanding of the relationship between PI availability and the turnover of subcellular PPIn pools. To address these shortcomings, we established a molecular toolbox for investigations of PI distribution within intact cells by exploiting the properties of a bacterial enzyme, PI-specific PLC (PI-PLC). Using these tools, we find a minor presence of PI in membranes of the ER, as well as a general enrichment within the cytosolic leaflets of the Golgi complex, peroxisomes, and outer mitochondrial membrane, but only detect very low steady-state levels of PI within the plasma membrane (PM) and endosomes. Kinetic studies also demonstrate the requirement for sustained PI supply from the ER for the maintenance of monophosphorylated PPIn species within the PM, Golgi complex, and endosomal compartments.

• MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• biosenzitivní techniky MeSH
• buněčná membrána metabolismus   MeSH
• Cercopithecus aethiops MeSH
• COS buňky MeSH
• fosfatidylinositolfosfáty metabolismus   MeSH
• fosfatidylinositoly metabolismus   MeSH
• fosfolipasy typu C genetika   metabolismus   MeSH
• HEK293 buňky MeSH
• intracelulární membrány metabolismus   MeSH
• kinetika MeSH
• konfokální mikroskopie MeSH
• lidé MeSH
• luminescentní proteiny genetika   metabolismus   MeSH
• rekombinantní fúzní proteiny genetika   metabolismus   MeSH
• systémy druhého messengeru MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• srovnávací studie MeSH
• Názvy látek
• bakteriální proteiny MeSH
• fosfatidylinositolfosfáty MeSH
• fosfatidylinositoly MeSH
• fosfolipasy typu C MeSH
• luminescentní proteiny MeSH
• rekombinantní fúzní proteiny MeSH