Tunicamycin Facts Sheet (main)

This mini website about Tunicamycin was prepared by a student of BioInformatics, the Open University.

alternate names: Tunicamycin
Source: Antibiotic useful in glycoprotein research. Inhibitor of N-linked glycosylation and the formation of N-glycosidic protein-carbohydrate linkages


Source: Tunicamycin is an antibiotic that blocks the reaction of UDP-GlcNAc and Dol-P in the first step of glycoprotein synthesis, thus inhibiting the synthesis of all N-linked glycoproteins



Lysosomes are membrane bound organelles filled with hydrolytic enzymes that the cell uses to digest various macromolecules. These macromolecules include proteins, polysaccharides, fats, and nucleic acids. Because these enzymes function optimally under acidic conditions, the lysosomal environment must be of a lower pH than the rest of the cell. This is accomplished through the pumping of hydrogen ions from the cytosol into the lumen of the lysosome.

The lysosomal associated membrane protein (LAMP-1) and Cathepsin D are both proteins found in the lysosome. While both proteins must travel to the lysosome after synthesis, the pathways they follow to their target destination are significantly different. Cathepsin D must first be glycosylated in the lumen of the endoplasmic reticulum (ER) in order to allow binding by mannose-6-phosphate to occur. The protein then travels to the Golgi apparatus for the consequent steps of glycosylation and must be bound by mannose-6-phosphate in order to attach itself to the mannose-6-phosphate receptor. In contrast, the LAMP-1 protein, although a heavily glycosylated protein, does not follow the mannose-6-phosphate protein targeting path.

Exposing cells to tunicamycin disrupts glycosylation of newly-synthesized proteins. This is due to the blockage of the transference of the 14 residue core oligosaccharide (containing two N-acetylglucosamine, nine mannose, and three glucose residues) from a dolichol phosphate donor molecule to certain asparagine (Asn) residues on the proteins. In the following investigation, cells treated with various concentrations of tunicamycin at differing incubation times are used to investigate the effects of glycosylation of newly-synthesized proteins on protein transportation.

If glycosylation does not have any effect upon LAMP-1, then LAMP-1 should reach its target organelle. Although LAMP-1 does not require glycosylation in order to be transported into the lysosome, tunicamycin treatment could alter the protein's tertiary structure, resulting in improper folding. If this occurs, LAMP-1 may be depolarized in either the ER or the Golgi apparatus. This should cause an accumulation of the protein in the ER. Lack of glycosylation and/or misfolding may also lead to protein degradation, in which case the protein would be destroyed and/or secreted. A loss of glycosylation should signify rapid degradation and eventual secretion of Cathepsin


  Tunicamycin and Brefeldin A induce in plant cells a programmed cell death showing apoptotic features




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