N-glycosylated proteins

In conclusion, the experimental evidence indicates that the mechanism of protein N-glycosylation in plants is very similar to that in animals, as a cotranslational event, occurring at the same subcellular location, and sensitive to the same antibiotics. 

Medzihradszky, K. F. Maltby, D. A. Hall, S. C. Settineri, C. A. Burlingame, A. L. 1994. Characterization of protein N-glycosylation by re versed-phase microbore liquid chromatography/electrospray mass spectrome-... 

Yan A, Lennarz WJ (2005), Unraveling the mechanism of protein N-glycosylation, J. Biol. Chem. 280 3121-3124. 

Roth J. 2002. Protein N-glycosylation along the secretory pathway Relationship to organelle topography and function, protein quality control, and cell interactions. Chem... 

Kukuruzinska, M.A. and Lennon, K. (1998) Protein N-glycosylation molecular genetics and functional significance. Crit. Rev. Oral Biol. Med. 9, 415-448. 

Figure 13 Protein N-glycosylation. (1) The formation of the donor substrate with 14 sugar units (Glc3Man9GlcNAc2-PP-dolichol) (2) the reaction scheme that shows the transfer of the tetradecasaccharyl group to the Asn residues found in the consensus sequence Asn-X-Ser/Thr in proteins (3) hydrolytic removal of the terminal sugar residues on the tetradecasaccharide and addition of more sugar units in the ER and Golgi. OSTase, oligosacchryltransferase.

Roth J. Protein N-glycosylation along the secretory pathway ... 

General Protein N-Glycosylation System in Campylobacter jejuni 353... 

Figure 3 Proposed pathway for protein N-glycosylation in Campylobacter jejuni.

Figure 12 Glycoengineering in Escherichia coii using Campylobacter jejuni protein N-glycosylation and N. meningitidis protein O-glycosylation systems. E. coli cells are transformed with a gene encoding a protein acceptor (purple), an OTase (yellow) and a gene cluster encoding the enzymes required for the synthesis of the glycan of interest.

Recently, a total serum protein N-glycosylation profiling was attempted on a CE chip by Ehrlich and coworkers [213]. The authors employed a glass chip with a double-tee injector and a 4% linear polyacrylamide sieving medium (analogous to nucleic acid separations). Profiling of serum samples from chronic hepatitis patients identified the differences in N-glycan composition in cirrhotic and noncirrhotic cases, and demonstrated the potential of microchip approach for these types of clinical studies. 

This proposal demonstrates that the sequence and conformation of the peptidal substrate can both play a critical role in protein N glycosylation. These factors combine to form a unique environment, providing the specificity and reactivity required to link an oligosaccharide to an asparagine carboxyamido nitrogen. Similar factors may play an important role in other protein processing reactions. 

In this reaction nucleotide sugars are the donor substrates (for some glycosyltransferases involved in the early stages of protein N-glycosylation a sugar-phosphate-dolichol is the donor molecule see later). In sequential reactions mono-... 

Figure 1. Initial steps in protein N-glycosylation. Pre-assembly of oligosaccharide-P-P-Dol and en bloc transfer to the protein in the endoplasmic reticulum. Dol, dolichol OST, oligosaccharyl-transferase P, phosphate , GlcNAc O, Man A, Glc.

Schallus, T Jaeckh, C Feher, K Palma, AS Liu, Y Simpson, JC et al. Malectin A Novel Carbohydrate-binding Protein of the Endoplasmic Reticulum and a Candidate Player in the Early Steps of Protein N-Glycosylation. Molecular Biology of the Cell, 2008, 19, 3404-14. 

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