​In eukaryotic cells, covalently attached lipids help to anchor some water-soluble proteins to the plasma membrane. One group of cytosolic proteins are anchored to the cytosolic face of membrane by a fatty acyl group (e.g. myristate or palmitate). These groups are generally covalently attached to which amino acids present at the N-terminus of the polypeptide chain?​

Correct option is A

Explanation-

Some proteins are lipid-modified (lipidated) at the N-terminal end to anchor them to membranes, especially the cytosolic face of the plasma membrane.

Myristoylation helps the protein associate with the plasma membrane or organelle membranes. Myristoylation involves myristic acid, a 14-carbon saturated fatty acid. It is covalently attached to the N-terminal glycine residue of a protein. This occurs co-translationally, after the initial methionine is removed, exposing glycine.

So, the correct answer is option a : Glycine — the amino acid to which myristoyl groups are covalently attached at the N-terminus of cytosolic proteins.

Incorrect options -

Option b - Tyrosine  -  May be involved in phosphorylation but not lipid anchoring at N-terminus
Option c - Serine  -  Target for palmitoylation or phosphorylation, but not myristoylation at N-terminus
Option d - Lysine  - Can undergo ubiquitination or acetylation, but not N-terminal fatty acid attachment