Which one of the following groups can be covalently attached

Which one of the following groups can be covalently attached to a protein in a living cell, insert into the hydrophobic interior of a membrane, and localize the protein to that membrane?

A. An ester-linked C20:4 fatty acid

B. A glycosylphosphatidylinositol at the C-terminus of the protein

C. An acyl chain amide linked to the side chain of a lysine in the protein

D. Diphosphatidylglycerol

E. An ester-linked cholesterol molecule

Solution

The option C will be the correct answer. Transmembrane proteins contain non polar amino acid residues with hydrophobic side chains that interact with fatty acyl groups of the membrane phospholipids. The acyl group of amide linked lysine can make a hydrophobic region , that can easily interact with the membrane hydrophobic region and helps the protein to stay in the membrane and the lysine is a charged amino acid that will peep out from the hydrophobic core and can easily interact with outer , charged , hydrophilic environment.