Cell-surface glycoprotein modification

The following protocols are generalized for the labeling of cell-surface glycoproteins or glycoproteins in solution. Some optimization may be necessary to achieve the best level of fluorescent modification for each particular application. 

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... 

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 biotinylated glycans on the cell surfaces subsequently may be probed with (strept)avidin reagents to detect the azido-sialic acid modifications. Alternatively, the cells may be lysed and the glycoproteins isolated using an immobilized (strept)avidin or monomeric avidin affinity resin. 

Bangs, J.D., Andrews, N.W., Hart, G.W., and Englund, P.T. (1986) Post-translational modification and intracellular transport of a trypanosome variant surface glycoprotein./. Cell Biol. 103, 255-263. 

Staudinger ligation and its traceless version have been explored in the preparation of glycoconjugates [70, 71]. It was used to label cell-surface carbohydrates [72, 73] and, more recently, to prepare glycoproteins by modification of L-azidohomoalanine-containing proteins [74, 75],... 

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