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TLS Online TPP Program

#Id: 7901

Deletions in mtDNA cause another set of diseases:
Chronic progressive external ophthalmoplegia
Kearns–Sayre syndrome

#Unit 2. Cellular Organization #Mitochondria #Part B Pointers
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TLS Online TPP Program

#Id: 7950

#Unit 2. Cellular Organization

Prior to transfer to a nascent chain in the lumen of the  ER, the oligosaccharide precursor is assembled on amembrane- attached anchor called dolichol phosphate, a longchain polyisoprenoid lipid
TLS Online TPP Program

#Id: 7951

#Unit 2. Cellular Organization

First sugar residue is attached to dolichol by a high-energy pyrophosphate linkage & the other sugars are added by glycosidic bonds
TLS Online TPP Program

#Id: 7952

#Unit 2. Cellular Organization

Two N- acetylglucosamine (GlcNAc) and five mannose residues are added one at a time to a dolichol phosphate on the cytosolic face of the ER membrane
TLS Online TPP Program

#Id: 7953

#Unit 2. Cellular Organization

Tunicamycin

blocks the first enzyme in this pathway, inhibits the synthesis of all N-linked oligosaccharides in cells.
TLS Online TPP Program

#Id: 7954

#Unit 2. Cellular Organization

The precursor oligosaccharide is transferred from a
dolichol lipid anchor to the asparagine as an intact unit in a reaction catalyzed by a transmembrane oligosaccharyl transferase enzyme complex.
TLS Online TPP Program

#Id: 7955

#Unit 2. Cellular Organization

Only asparagine residues in the tripeptide sequences Asn-X-Ser and Asn-X-Thr (where X is any amino acid except proline) are substrates for oligosaccharyl transferase.