Cell-surface glycoproteins, glycosylation

There are many glycosylation mutants of cultured mammalian cells and yeast. They have been selected as rare survivors of treatments that kill cells expressing a particular carbohydrate or glycoprotein at the cell surface. For example, plants produce a variety of proteins, called lectins, which bind to cell surface oligosaccharides. Lectins are toxic to mammalian cells. They can be used to select for mutants that no longer bind the lectin because they lack a particular carbohydrate at the cell surface. Such glycosylation mutants have low amounts of glycoproteins that require carbohydrates for stable expression. 

Although many proteins contain the modB carbohydrate, most of the attention has been on the analysis of two of them. One is a cell surface glycoprotein, called PsA (a.k.a. SP29), which has been cloned and sequenced. The carbohydrate modifications are located on a repeated motif, PTVT as shown by Edman degradation [68]. This sequence is typical of many of those in mammalian cell proteins which also contain O-Iinked oligosaccharides [69]. Several allelic variants of this protein from related strains of Dictyostelium discoideum contain 3-5 of these glycosylated repeats [70]. This protein... 

The effects of retinoids on the synthesis of fibronectin are well documented (Hassell etal, 1978 Jetten, Jetten and Sherman, 1979b Jetten etal, 1979a Patt et al, 1978), but the exact relationship is not fully understood. There might be direct effects via the glycosylation and consequent protection of fibronectin and indirect effects by way of glycosaminoglycan or cell surface glycoprotein synthesis, which leads to feed-back influences on the production of fibronectin. 

Glycosylation is one of the most important PTM of proteins (14P525). Several studies report that modifications of cell surface glycoproteins are a hallmark in several diseases and are prominent and aberrant processes in... 

The change in the authorship of this chapter has led to a few alterations in its construction. Because of their importance, cell-surface glycoproteins have been reviewed separately some glycosylated proteins that would have previously been included in the sections extending from microbial to animal polysaccharides may now be lodged in this new section. 

Following the observation that proteins located on the external surface of human erythrocyte membranes contain carbohydrate, lactoperoxidase-catalysed iodination has been used to label the external surface of human tumour KB cells. Only a relatively small number of protein subunits of the plasma membrane were accessible to enzymic iodination, and most, if not all, of these molecules appear to be glycosylated. A cell-surface glycoprotein containing a D-galactosyl residue at the non-reducing terminus has been isolated from culture fluids of I29/J mouse ascites teratoma cells, and it may be responsible for cell-to-cell adhesion. ... 

Asada, M., Furukawa, K., Segawa, K., and Kobata, A., 1992, Biological significance of altered glycosylation of the cell surface glycoproteins in the transformed cells, Cell Struct. Funct. VhAll (Abstract). 

Bednarski has reported that this allylation reaction has been used for the key step in the synthesis of C-glycoside derivatives of sialic acids, which are the carbohydrate groups found at the terminal sites of cell-surface glycoproteins and glycolipids. Thus, the allylation of glycosyl chloride 16 with allyltributyltin under photo irradiation in the presence of hexabutylditin followed by hydrolysis gives an approximate 1 1 mixture of the a- and P-isomers. It is worth mentioning that while several synthetic approaches by... 

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