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. Involved in non-vesicular transport of ergosterol and PI(4)P at the NVJ. Binds sterol and PI4P in a mutually exclusive manner. May be involved in formation of PMN vesicles by altering the membrane lipid composition.
Subcellular Localization:
Golgi apparatus membrane. Nucleus outer membrane. Endoplasmic reticulum membrane. Vacuole membrane. Note=Soluble protein that accumulates on the surface of late Golgi membranes and at nucleus-vacuole (NV) junctions, interorganelle interfaces between the nuclear envelope and the vacuole membrane formed during piecemeal microautophagy of the nucleus (PMN). Targeted exclusively to NV junctions in stationary phase.
Domain:
The ankyrin repeats are required for targeting the protein to the NV junction by interacting with NVJ1; The PH domain strongly binds to phosphoinositides and is required for targeting the protein to the late Golgi membranes; The FFAT (two phenylalanines in an acidic tract) motif is required for interaction with SCS2 and is required for targeting the protein to the ER; 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:
MEQPDLSSVAISKPLLKLKLLDALRQGSFPNLQDLLKKQFQPLDDPNVQQVLHLMLHYAVQVAPMAVIKEIVHHWVSTTNTTFLNIHLDLNERDSNGNTPLHIAAYQSRGDIVAFLLDQPTINDCVLNNSHLQAIEMCKNLNIAQMMQVKRSTYVAETAQEFRTAFNNRDFGHLESILSSPRNAELLDINGMDPETGDTVLHEFVKKRDVIMCRWLLEHGADPFKRDRKGKLPIELVRKVNENDTATNTKIAIDIELKKLLERATREQSVIDVTNNNLHEAPTYKGYLKKWTNFAQGYKLRWFILSSDGKLSYYIDQADTKNACRGSLNMSSCSLHLDSSEKLKFEIIGGNNGVIRWHLKGNHPIETNRWVWAIQGAIRYAKDREILLHNGPYSPSLALSHGLSSKVSNKENLHATSKRLTKSPHLSKSTLTQNDHDNDDDSTNNNNNKSNNDYDDNNNNNNNDDDDYDDDDESRPLIEPLPLISSRSQSLSEITPGPHSRKSTVSSTRAADIPSDDEGYSEDDSDDDGNSSYTMENGGENDGDEDLNAIYGPYIQKLHMLQRSISIELASLNELLQDKQQHDEYWNTVNTSIETVSEFFDKLNRLTSQREKRMIAQMTKQRDVNNVWIQSVKDLEMELVDKDEKLVALDKERKNLKKMLQKKLNNQPQVETEANEESDDANSMIKGSQESTNTLEEIVKFIEATKESDEDSDADEFFDAEEAASDKKANDSEDLTTNKETPANAKPQEEAPEDESLIVISSPQVEKKNQLLKEGSFVGYEDPVRTKLALDEDNRPKIGLWSVLKSMVGQDLTKLTLPVSFNEPTSLLQRVSEDIEYSHILDQAATFEDSSLRMLYVAAFTASMYASTTNRVSKPFNPLLGETFEYARTDGQYRFFTEQVSHHPPISATWTESPKWDFYGECNVDSSFNGRTFAVQHLGLWYITIRPDHNISVPEETYSWKKPNNTVIGILMGKPQVDNSGDVKVTNHTTGDYCMLHYKAHGWTSAGAYEVRGEVFNKDDKKLWVLGGHWNDSIYGKKVTARGGELTLDRIKTANSATGGPKLDGSKFLIWKANERPSVPFNLTSFALTLNALPPHLIPYLAPTDSRLRPDQRAMENGEYDKAAAEKHRVEVKQRAAKKEREQKGEEYRPKWFVQEEHPVTKSLYWKFNGEYWNKRKNHDFKDCADIF