Phosphated glycans

N., Leon, V, and Pujol, J.P. An inositol-phosphate glycan released by TGF-beta mimics the proliferative but not the transcriptional effects of the factor and requires functional receptors. Cell Signal,... 

Alvarez, L, Avila, M. A., Mato, J. M., Castano, J.G., and Varela-Nieto, I. Insulin-like effects of inositol phosphate-glycan on messenger RNA expression in rat hepatocytes. Mol. Endocrinol., 1991, 5, 1062-1068. 

Misek, D.E. and Saltiel, A.R. An inositol phosphate glycan derived from a Trypanosoma brucei glycosyl-phosphatidylinositol mimics some of the metabolic actions of insulin. J. Biol. Chem., 1992, 267, 16266-16273. 

CRD cross-reacting determinant IPG inositol phosphate glycan... 

Note. When the linkage between monosaccharide units is non-glycosidic (as in the phosphate derivative shown below), use of the glycan terminology is inappropriate other methods of polymer nomenclature should be employed [20],... 

Wallace A., Boyce J., and Balland A. (2002), Structural Characterization of Man-nose-6-phosphate-containing glycans by tandem mass spectrometry, IBC s Conference on The Impact of Post-Translational and Chemical Modifications on Protein Therapeutics, San Diego, CA. 

For the study of polyprenyl glycosyl phosphates as intermediates in the synthesis of complex glycans, several techniques have been developed, and these have been described elsewhere in detail.18 20 Two important features should be emphasized. First, the very small amounts of polyprenyl phosphates that are present in most tissues for this reason, the use of radioactive techniques for the detection of products is obligatory. Second, on account of the hydrophobic nature of these compounds, and as the enzymes involved in the reactions are membrane-bound, the use of detergents and organic solvents becomes necessary. 

Fig. 3. Schematic of staining process of SARS-CoV immunochip. (1) Spotting A high-precision robot transfers the samples, SARS-CoV proteins, and glycans of various complexities, from 96-well plate to nitrocellulose-coated glass slides. (2) Staining Before staining, the slides are rinsed with IX phosphate-buffered saline (PBS), and blocked with 1% bovine serum albumin (BSA)-PBS containing 0.05% NaN3 and 0.05% Tween-20. They are subsequently incubated with horse anti-SARS sera. The primary antibodies captured by microarrays are detected using biotinated anti-horse immunoglobulin (Ig)G, and visualized by Cy3-streptavidin.

Another metal present in biological media in relatively high concentrations is iron. Most iron ions are strongly coordinated within proteins, although a small fraction of iron ions is loosely bound with carboxylates and phosphates, phospholipids, glycans, and sulphonates. This fraction is usually called labile iron and constitutes a pool of iron ions accessible for incorporation into functional metalloproteins. In contrast to closed shell cations, rather than increasing the fluorescence quantum... 

The specificity is such that it is entirely feasible that the action of such an enzyme is to release a glycan-inositol phosphate compound. However, the nature and mechanism of action of such a compound have yet to be resolved. 

Fig. 4. Proposed production of a glycan-inositol phosphate mediator by insulin. This summarizes Sal-tiel and Cuatrecasas concept for the production of novel mediators through insulin s action. It may, by analogy with the receptor-mediated stimulation of inositol phospholipid metabolism, involve a G-pro-tein. Here it is postulated that the putative Glns may play such a role.

Traditional methods to map posttranslational modification sites, like those of phosphorylation, have been anchored by protein digest and mass spectroscopic (MS) approaches (for a review on the classic evaluation and for MS analyses of O-glycans, see Reference (56)). Unfortunately, like many posttranslational modifications, O-GlcNAcylation occurs routinely on a protein population with substoichiometric frequency, which results in a very small detectable population of a O-GlcNAc-modified product. Also, much like O-phosphate additions, the protein-O-GlcNAc bond is labile and is detached by collision-induced dissociation (CID) during MS analysis. Often, the bond is lost before it can be detected on the peptides analyzed (57, 58). Phosphate modifications, however, can overcome this limitation by emiching the peptide mixtures... 

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