Question

Apolipoprotein E is rich in which amino acid?

• A. Lysine
• B. Arginine
• C. Histidine
• D. Methionine

Hint:

Apo-E is the arginine-rich apoprotein of VLDL.

Answer 1

The Correct Option is B

Step 1: The target molecule is apo-E, a key ligand on VLDL and chylomicron remnants that lets the liver clear them through the LDL and LRP receptors.

Step 2: A long standing nickname for apo-E is the arginine-rich apoprotein, because of the unusually high proportion of arginine residues in its sequence.

Step 3: Putting numbers to it, arginine contributes close to one tenth of all amino acids in the protein, and apo-E itself forms about 5 to 10 percent of VLDL protein in healthy individuals.

Step 4: By elimination, lysine, histidine and methionine do not characterise apo-E, so the basic, guanidinium-bearing arginine is the answer.

\[\boxed{\text{Arginine}}\]