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. Binds and transports sterol. 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 1069 molecules/cell in log phase SD medium.
Subcellular Localization:
Cell membrane; Peripheral membrane protein. Endoplasmic reticulum membrane. Note=Cell periphery, enriched in small buds of G1 phase cells and near the bud-neck region of S phase cells. Enriched on regions of the ER in close proximity with the plasma membrane (PM), which may represent PM-ER membrane contact sites (MCS).
Domain:
The PH domain strongly binds to phosphoinositides and is required for targeting the protein to the membrane; 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.
Sequence:
MSREDLSIAEDLNQVSKPLLKVKLLEVLGQGDFKHLKALVDNEFQPKDDPSVQQVLNLILHYAVQVAPILLIKEIVAHWVDQVGDEKSSSKSDDGIHLDLNYQDENGNTPLHLAAAQSRSDVISFLLSQKSINDCVKNKAHQQPLDMCKDLNVAQMIQLKRDDYFLETVHSLRAAMNKRDFSKLDSIWKNPRNLNLLDINGIDPETGTTLLYEYSQKKDIEMCQWLLKHGAEATVKDGKGRSPLDLVKNIKLPAKPSNNVTPEIKLKNLLEKNLREQAIVHEDVASSKPPTYKGFLKKWTNFAHGYKLRWFILSGDGNLSYYKDQSHVDRPRGTLKVSTCRLHIDSSEKLNFELLGGITGTTRWRLKGNHPIETTRWVNAIQSAIRFAKDKEILNKKKAVPPSLALKNKSPALISHSKTQGSLPEASQYYQHTLHKEVIQPSSVSLYRRPSNNLSVVSSEIQLNDNLTESGKRFVSKMIENRLDGSKTPVGVHTGSALQRVRSSNTLKSNRSMQSGSGVASPIDKVPNGANLSQSNTTTGSTASLSDNNYIDNFEGDEANSDDEEEDLGINFDRDEEYIKAQYGPYKEKLDMYEQAISIELSSLIELIEQEEPSPEVWLTIKKSLINTSTIFGKLKDLTYKRDKRLVDMVSKQGDVNNVWVQSVKELEMELSNKTERLASIDKERRGLKKILHKKLLESHATAGNKESLENDKEQESDTTASTLGQIAKFISATKEEDEASDADEFYDAAELVDEVTELTEAHPEISTAAAPKHAPPPVPNETDNDSQYVQDEKSKIESNVEKTSQKFEKQNNLVTEDEPKTDQSLKNFKAEDKESQVKEKTKEIASSVIGEKTIVAVTTVQKRKEEYLLKEGSYLGYEDGIRKRLSMDKDDRPKISLWAVLKSMVGKDMTRMTLPVTFNEPTSLLQRVAEDLEYSELLDQAATFEDSTLRTLYVAAFTASSYASTTKRVAKPFNPLLGETFEYSRPDKQYRFFTEQVSHHPPISATWTESPRWDFWGESFVDTKFNGRSFNVKHLGLWHIKLRPNDNEKEELYTWKKPNNTVIGILIGNPQVDNHGEVNVVNHTTGDHCKLYFKARGWRSSGAYEITGEVYNKKKQKVWILGGHWNEAIFAKKVVKDGDLSLEKTRTAASAGNGPTDDGTKFLIWKANDRPEEPFNLTPFAITLNAPQPHLLPWLPPTDTRLRPDQRAMEDGRYDEAGDEKFRVEEKQRAARRKREENNLEYHPQWFVRDTHPITKAKYWRYTGKYWVKRRDHDLKDCGDIF