Q30. Amino acids responsible for N-linked and O-linked glycosylation of proteins are
The correct answer is (D) Asparagine and Threonine.
N-linked glycosylation attaches oligosaccharides to the nitrogen atom on asparagine’s side chain in the ER, while O-linked glycosylation attaches them to the hydroxyl oxygen on threonine (or serine) in the Golgi.
Option Analysis
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(A) Asparagine and Aspartic acid: Asparagine is correct for N-linked via its amide group, but aspartic acid (with a carboxylic acid side chain) does not participate in either major glycosylation type.
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(B) Glutamine and Serine: Glutamine’s side chain is similar to asparagine but lacks the specific recognition for N-linked glycosylation; serine handles O-linked, not paired here.
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(C) Glutamic acid and Serine: Glutamic acid (acidic side chain) is uninvolved; serine supports O-linked but not with glutamic acid.
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(D) Asparagine and Threonine: Correct. Asparagine for N-linked (Asn-X-Ser/Thr motif), threonine for O-linked (GalNAc addition).
Article:
In protein biochemistry, glycosylation modifies proteins by adding sugars, with N-linked and O-linked types targeting specific amino acids responsible for N-linked and O-linked glycosylation of proteins. This post solves GATE Life Sciences Q30, explaining each option for competitive exam success.
N-Linked Glycosylation Basics
N-linked glycosylation occurs co-translationally in the ER, linking Glc3Man9GlcNAc2 to asparagine (Asn) in the Asn-X-Ser/Thr sequence (X ≠ Pro). Asparagine’s amide nitrogen forms the N-glycosidic bond, aiding folding and trafficking.
O-Linked Glycosylation Basics
O-linked glycosylation happens post-translationally in the Golgi, attaching GalNAc to threonine (Thr) or serine (Ser) hydroxyl groups via O-glycosidic bonds. It’s common in mucins and signaling proteins.
Q30 Full Solution
Amino acids responsible for N-linked and O-linked glycosylation of proteins are asparagine (N-linked) and threonine (O-linked), making (D) correct. Other options mismatch targets.
| Option | Amino Acids | Glycosylation Role | Correct? |
|---|---|---|---|
| (A) | Asparagine, Aspartic acid | N-linked (Asn only) | No |
| (B) | Glutamine, Serine | O-linked (Ser only) | No |
| (C) | Glutamic acid, Serine | None for Glu | No |
| (D) | Asparagine, Threonine | N & O-linked | Yes |
Master these for GATE Life Sciences—key phrase “amino acids responsible for N-linked and O-linked glycosylation” boosts your prep!
1 Comment
Ankita Pareek
April 18, 2026Arginine for N linked glycosylation which takes place in ER co translationally whereas threonine for o linked glycosylation which takes place in golgi post translationally