Glycosylphosphatidylinositol moiety

A bacterial phosphatidylinositol specific phospholipase C (PI-PLC) had been available for many years before it was demonstrated to strip a number of membrane-bound proteins from eukaryotic cell surfaces [1], Such proteins are anchored by a PI moiety in which the 6 position of inositol is glycosidically linked to glucosamine, which in turn is bonded to a polymannan backbone (Fig. 3-10). The polysaccharide chain is joined to the carboxyl terminal of the anchored protein via amide linkage to ethanolamine phosphate. The presence of a free NH2 group in the glucosamine residue makes the structure labile to nitrous acid. Bacterial PI-PLC hydrolyzes the bond between DAG and phosphati-dylinositols, releasing the water-soluble protein polysac charide-inositol phosphate moiety. These proteins are tethered by glycosylphosphatidylinositol (GPI) anchors. 

Furthermore, according to Howell and Crine (1996), type IV represents multimers of subunits, type V represents proteins that are anchored to the membrane by a covalently linked lipid moiety only, and type VI represents those anchored both by a transmembrane domain and the glycosylphosphatidylinositol (GPI) anchor (see Section III,C,3). 

The uPAR protein was initially purified from lysates of phorbol ester-stimulated U937 cells by affinity chromatography using diisopropyl fluoro-phosphates (DFP)-inactivated uPA [53, 54]. uPAR is anchored in the plasma membrane by a glycosylphosphatidylinositol (GPI) moiety and it consists of 283 amino acids in its processed form [55, 56]. The protein is composed of three domains and each domain contains 90 amino acids. The domains are connected by linker regions with a length of 15-20 amino acids [57, 58]. The disulfide bonds in the N-terminal domain I have been experimentally determined and the pattern of cysteine residues in the sequence has revealed... 

Glycosylphosphatidylinositols are naturally occurring glycophospholipids on a cell surface. Full structural assignment was reported by Ferguson et al. in 1988 [142,143]. The core structure was composed of a carbohydrate residue with an ethanolamine side chain, inositol residue, and a phosphoglycerolipid residue (O Fig. 11). The carbohydrate residue, ethanolamine side chain or lipid moiety is species specific [144,145,146,147,148], and depends on species and... 

N. Heise, M. L. Cardoso de Almeida, and M. A. J. Ferguson, Characterization of the hpid moiety of the glycosylphosphatidylinositol anchor of Trypanosoma cruzi lG7-antigen, Mol. Biochem. Parasitol., 70 (1995) 71-84. 

Glycosylphosphatidylinositol (GPI) anchors are found in many cell surface proteins in eukaryotes, which tether them to the extracellular side of the plasma membrane. The GPI anchor is attached to the C-terminus of a protein via a phosphoetha-nolamine linkage. GPIs and GPI-anchored proteins are built up in the ER and then the modified proteins transit to the cell surface. This posttranslational glyco-lipid modification is mediated by the GPI transamidase (GPI-T) in the ER lumen. The GPI anchor can be hydrolysed by phosphatidylinositol-specific phospholipase C or D (PLC or PLD) which releases the protein moiety into the extracellular milieu... 

Reversed-phase HPLC-TSP-MS was used by Biitikofer et al. (1990) for the determination of glycerobenzoate derivatives of diradylglycerols of phospholipids. Neither intact phospholipids nor classes of polar lipids were determined. The PI moiety of the glycosylphosphatidylinositol (GPI)... 

A novel approach for the synthesis of bioactive glycosylphosphatidylinositols (20) and (21), that contain an unsaturated fatty acid in the lipid moiety, exploits the use of a non benzyl-type protecting group/ ... 

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