Question

Which statement best describes the initial process of N-linked glycosylation in the endoplasmic reticulum

Answer 1

Answer:

The oligosaccharide is assembled on the lipid carrier at the membrane of the ER

Explanation:

N-linked glycosylation consists of the attachment of an oligosaccharide (glycan) to a nitrogen atom of the asparagine (Asn) residue in the protein. N-linked glycosylation is a key posttranslational modification (PTM) capable of controlling protein structure and function, this pathway takes place in the plasma membrane in archaea organisms and in the membranes of the endoplasmic reticulum (ER) in eukaryotic organisms. In eukaryotic cells, the N-linked glycosylation conserved pathway consists of two steps. In the first place, the oligosaccharides are assembled on a lipid carrier called dolichyl pyrophosphate localized in the endoplasmic reticulum (ER). The dolichyl-phosphatase is a hydrolase enzyme that acts on phosphoric monoester bonds. Second, the oligosaccharides are modified by specific glycosyltransferases that transfer these molecules to selected Asparagine (Asn) acceptor residues of polypeptide chains that have entered the lumen of the ER. These N-glycans are firstly assembled as a dolichol-linked precursor oligosaccharide at the cytoplasmic face of the ER.