The following text describes a protein:
Function:
Lipid transport protein (LTP) involved in non-vesicular transfer of lipids between membranes. Functions in phosphoinositide-coupled directional transport of various lipids by carrying the lipid molecule in a hydrophobic pocket and transferring it between membranes through the cytosol. Involved in maintenance of intracellular sterol distribution and homeostasis. May serve as a sensor of PI4P levels at PM-ER membrane contact site, regulating PI4P phosphatase SAC1 activity. May be involved in ergosterol transport from the plasma membrane (PM) to the ER, however it does not bind sterols directly. Plays a role in the positive regulation of vesicular transport of ceramide from the ER to the Golgi, negatively regulating COPII-mediated ER export of cargos.
Miscellaneous:
MISCELLANEOUS: Present with 589 molecules/cell in log phase SD medium.
Subcellular Localization:
Cytoplasm. Endoplasmic reticulum membrane. Note=Enriched at the cell periphery in a SCS2-dependent manner. Enriched on regions of the ER in close proximity with the plasma membrane (PM), which may represent PM-ER membrane contact sites (MCS). Localizes to PM-ER membrane contact sites dependent upon PM PI4P levels.
Domain:
The GOLD (Golgi dynamics) domain is predicted to mediate diverse protein-protein interactions; The PH domain weakly binds to phosphoinositides; The FFAT (two phenylalanines in an acidic tract) motif is required for interaction with SCS2 and proper localization of the protein; The OSBP-related domain (ORD) mediates binding of sterols and phospholipids. It displays an incomplete beta-barrel containing a central hydrophobic tunnel that can accommodate a single lipid molecule with a flexible lid covering the tunnel entrance. The ORD can bind two membranes simultaneously. It has at least two membrane-binding surfaces; one near the mouth of the lipid-binding pocket and a distal site that can bind a second membrane. These structural features correlate with the phosphatidylinositol 4-phosphate (PI(4)P)-coupled lipid transport optimized in closely apposed membranes, such as organelle contact sites. The lipid transfer cycle starts from the association of the LTP with a donor membrane, which accompanies conformational changes that uncover the ligand-binding pocket. The tunnel opening is generally mediated by displacement of the lid covering the binding pocket allowing uptake or release of a lipid molecule. The LTPs extract the lipid from the membrane by providing a hydrophobic environment as well as specific interaction. Dissociation from the donor membrane shifts the conformation to a closed form. Then, the LTPs loaded with a cargo lipid diffuse through the aqueous phase. Lid opening may be induced by the interaction of a hydrophobic side of the lid with the target membranes (Probable). The OSH3 ORD does not accept sterols due to the small hydrophobic tunnel.
Sequence:
METIDIQNRSFVVRWVKCGRGDVINYQIKPLKKSIEVGIYKKLKSSVDDHASAVHIAPDTKTLLDYTTKSLLHKGSSSNIEEHHRRSSQHSHSSSNGSDNKRKERSYSSLSISGIQQQSQEIPLREKLSASGFTLVKRVGNVSGNTMVQGDLEVKDTDYYYAFILDNSSSKNAKKKILFNASVINGDNQSMISTRSTPPARPTALSRTSTQQDMLFRVGQGRYLQGYLLKKRRKRLQGFKKRFFTLDFRYGTLSYYLNDHNQTCRGEIVISLSSVSANKKDKIIIIDSGMEVWVLKATTKENWQSWVDALQTCFDDQFEDKDTSTLEENPDILDDDKEVINKSSPQDHDHLTPTATTKSALSHRQHTQKDMDDIYVPLPSESYATFSMNLRLIQQRLEQCKKDSLSYKPTTLHQRSEGLNGTHSSSSVFTNNRVSSFNHSSSGMTSSDSLASEEVPSNKTYIEHALYNQLADLEVFVSRFVTQGEVLFKDHQILCKKAKDTRVSLTSYLSENDEFFDAEEEISRGVIILPDTEDDINNIVEETPLLGKSDQNEFTKEVQLSGSEQIASSSVESYTTNDENHSRKHLKNRHKNRRRGHPHHQKTKSAQSSTETFTSKDLFALSYPKSVTRRNDIPEAAASPPSLLSFLRKNVGKDLSSIAMPVTSNEPISILQLISETFEYAPLLTKATQRPDPITFVSAFAISFLSIYRDKTRTLRKPFNPLLAETFELIREDMGFRLISEKVSHRPPVFAFFAEHLDWECSYTVTPSQKFWGKSIELNNEGILRLKFKTTGELFEWTQPTTILKNLIAGERYMEPVNEFEVHSSKGDKSHILFDKAGMFSGRSEGFKVSIIPPPSSNRKKETLAGKWTQSLANETTHETIWEVGDLVSNPKKKYGFTKFTANLNEITEIEKGNLPPTDSRLRPDIRAYEEGNVDKAEEWKLKLEQLQRERRNKGQDVEPKYFEKVSKNEWKYITGPKSYWERRKKHDWSDISQLW