Binding of ligand to predimerized but inactive RTK alters the conformation of the dimer in such a way that the receptor’s kinase becomes activated.

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.

TLS Online TPP Program

#Id: 7956

#Unit 2. Cellular Organization

A branched oligosaccharide containing 

3 glucose (Glc)

9 mannose (Man)

2 N-acetylglucosamine (GlcNAc)

Glc3Man9(GlcNAc)2

TLS Online TPP Program

#Id: 7957

#Unit 2. Cellular Organization

Immediately after the entire precursor, Glc3Man9(GlcNAc)2 is transferred to a nascent polypeptide, three different enzymes, called  glycosidases, remove all three glucose residues and one particular mannose residue.

TLS Online TPP Program

#Id: 7958

#Unit 2. Cellular Organization

The efficient formation of disulfide bonds in the lumen of the ER depends on the enzyme protein disulfide isomerase (PDI), which is present in all eukaryotic cells