Glycosylation sequencing

Structure—function relationships of prolactin among a variety of species have been pubUshed (17,18). Only one gene for prolactin appears to exist (19). Although classically placed in the category of simple protein hormones, prolactin can be glycosylated. Carbohydrate attachment occurs at Asn-31, where the consensus glycosylation sequence Asn—X—Ser is found. 

All of the known class A receptors are subject to posttranslational modification at one or more iV-linked glycosylation sequences, found either in the extracellular amino terminns or in the second exdacellular loop. Glycosylation is required for the expression of some GPCRs at the plasma membrane (12,13). Furthermore, many receptors, snch as rhodopsin and the dopamine receptors, are also subject to other posttranslational modifications, such as palmitoylation at the intracellular domains... 

Molecular weight Glycosyl sequence in oligo- and poly-saccharides... 

M. Nur-e-Alam, C. Mendez, J. A. Salas, and J. Rohr, Elucidation of the glycosylation sequence of mithramycin biosynthesis Isolation of 3A-deolivosylpremithramycin B and its conversion to premithramycin B by glycosyltransferase MtmGII, Chembiochem., 6 (2005) 632-636. 

P, NH2-terminal signal peptide (synthesis and translocation into the endoplasmic reticulum) NH2-terminal D-domains (oligomerization/multimerization -interdimer bonds-, N-glycosylation) Partially repeated or non repeated O-Glycosylated sequences (O-glycosylatlon, sulphatlon)... 

Scheme 9. The Five-step Glycosylation Sequence in the Synthesis of ent- C104...

Compound 100-2 (241, 12b-L-rhodinosylaquayamycin), isolated from a blocked mutant of the urdamycin producer Streptomyces fradiae Til 2717, represents the missing link in the glycosylation sequence of the urdamycins [164]. Structure 241 proves that the linkage of the L-rhodinose at C-12b-0 is the first of three 0-glycosylation steps (after the C-glycosylation of one olivose several biosynthetic steps before, see Sect. 10). 

Klich et al. have also accomplished the synthesis of extensively glycosylated sequences of glycophorin A containing the Tn antigen [96] (O Scheme 14). 

Lee EU, Roth J Paulson JC (1989) Alteration of terminal glycosylation sequences on N-linked oligosaccharides of Chinese hamster ovary cells by expression of beta-galactosidase alpha 2,6-sialyltransferase. Journal of Biological Chemistry 264 13848-13855. 

Other uses for glycosylamides have also been described in the literature. Amphiphilic glycosylamides have been demonstrated to be a valuable class of non-ionic biosurfactants (/O). Also, Kunz has used N-glycosylamides as an anomeric protecting group in glycosylation sequences (4). 

The current commercially available instruments offer a variety of features in terms of their scale (15 mg to 5 kg of resin), chemical compatibility with 9-fluorenylmethyloxycarbonyl/terf-butyl (Fmoc/tBu) and tert-butyloxycarbonyl/ benzyl (Boc/Bzl)-based methods, software (reaction monitoring and feedback control), and flexibility (additional washing and multiple activation strategies). In addition, certain instruments are better suited for the synthesis of more complex peptides such as cyclic, phosphorylated, and glycosylated sequences while others possess the ability to assemble a large number of peptide sequences. The selection of an instrument is dependent on the requirements and demands of an individual laboratory. This chapter will describe the features of the currently available systems. 

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