Question

[please briefly explain and answer]

A recently developed strain of rabbits had a mutation in the binding region of apolipoprotein B (apo-B) which severely affected its interaction with receptors. What do you expect to result in the metabolism of the plasma lipoproteins as a consequence of this mutation? Explain. The main function of apo-B is to interact with the receptors for the uptake of LDL and chylomicron remnants.

Answer 1

Apolipoprotein B is one of the largest polypeptide chain of more than 4500 amino acids .It has following two main functions

1. It is the primary protein responsible for organisation of the structural component of LDL particles. It has two variants Apo B-100 and Apo B-48.

2. Apo B is also responsible for internelization of low density lipids via receptor mediated endocytosis by binding with LDL receptor.

Now Since the mutation in apo B is in only that part of the protein which binds with LDL receptor. So this mutation will not hamper the structural role but receptor mediated endocytosis will not happen. Hence, concentration of LDL in blood will remain continuously high (because intake of LDL is not happening since LDL receptor can not bind ). Continuously high LDL+ apoB in blood will trigger plaque formation and ultimately lead to atherosclerosis. The rabbit will suffer from high blood pressure and cardio vascular diseases.