N-linked glycosylation

Fig. 1. Hypothetical secondary structure of a human plasma membrane Na /H exchanger. (Adapted from Sardet et al. [53].) Shaded bars, putative transmembrane segments. Hatched bars, putative amphipathic helices (numbers at tops and bottoms of bars refer to positions of amino acids). CHO, possible site of N-linked glycosylation. Solid bars, regions of the porcine renal Na /H exchanger used for immunolocalization in LLC-PK cells.

Chabot DJ, Chen H, Dimitrov DS, Broder CC. N-Linked glycosylation ofCXCR4 Masks coreceptor function for CCR5-dependent human immunodeficiency vims type 1 isolates. J Virol 2000 74(9) 4404-4413. 

Fig. 8.1 Hypothetical two-dimensional model of human P-glycoprotein. Small circles amino acid residues large circles ATP sites squiggly lines N-linked glycosylation sites (modified from [15]).

N-linked glycosylation is sequence specific, involving the transfer of a pre-synthesized oligosaccharide chain to an asn residue found in a characteristic sequence Asn-X-Ser, or Asn-X-Thr or Asn-X-Cys, where X represents any amino acid residue, with the exception of proline. An additional glycosylation determinant must also apply, as not all potential N-linked sites are glycosylated in some proteins. The pre-synthesized oligosaccharide side chain then undergoes... 

Imperiali, B. and O Connor, S. 1999. Effect of N-linked glycosylation on glycopeptide and glycoprotein structure. Current Opinion in Chemical Biology 3(6), 643-649. 

M-CSF serves as a growth, differentiation and activation factor for macrophages and their precursor cells. It is also known as CSF-1. This cytokine is produced by various cell types (Table 10.5). The mature form is a glycoprotein containing three potential N-linked glycosylation sites. Three related forms of human M-CSF have been characterized. All are ultimately... 

Incomplete (N-linked) glycosylation prompts decreased in vivo activity due to more rapid hepatic clearance of the EPO molecule. Enzymatic removal of terminal sialic acid sugar residues from oligosaccharides exposes otherwise hidden galactose residues. These residues are then free to bind specific hepatic lectins, which promote EPO removal from the plasma. The reported plasma tm value for native EPO is 4-6 h. The tm for desialated EPO is 2 min. Comparison of native human EPO with its recombinant form produced in CHO cells reveals very similar glycosylation patterns. 

Human TPO is a 332 amino acid, 60 kDa glycoprotein, containing six potential N-linked glycosylation sites. These are all localized towards the C-terminus of the molecule. The N-terminal half exhibits a high degree of amino acid homology with EPO and represents the biologically active domain of the molecule. 

N-linked glycosylation Removal of mannose Removal of two glucoses... 

Ausubel, I., Frederick, M. (eds.), Current Protocols in Molecular Biology, Unit 17.10 Inhibition of N-Linked Glycosylation, John Wiley Sons (1993). 

In transit through the ER and Golgi, the proteins acquire oligosaccharide side chains attached commonly at serine or threonine residues (O-linked) or at asparagine residues (N-linked). N-linked glycosylation requires participation of a special lipid called dolichol phosphate. 

Asparagine is a site for N-linked glycosylation of proteins, a posttranslational modification that should be associated with the endoplasmic reticulum. 

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