Question

What two types of receptors are involved in receptor mediated endocytosis, and what types of substances are their “ligands”? What function does receptor mediated endocytosis play for each type of receptor?

Answer 1

Receptor mediated endocytosis is a form of endocytosis in which receptor proteins on the cell surface are used to capture a specific target molecule.the receptors which are trans membrane proteins,cluster in regions of plasma membrane.

Two types of receptors involved in receptor mediated endocytosis are

1 - LDL receptor - (low density Lippo protein receptor) is a mosaic protein of 839 amino acids. Its main function is to mediate the endocytosis of cholestrol rich LDL and thus maintaining plasma level of LDL. They are clustered in clatherin coated pits.This occurs in nucleated cells mainly in liver.After internalisation they disociate from their ligand in lower pH.

A cell surface LDL receptor binds to an ApoB protein embeded in the phospholipid bilayer of an LDL particle forming receptor ligand complex

2 - Transferrin receptor - is a carrier protein for transferrin, a major glyco protein in blood.Its main function is to transfer iron in to all tissues cells from the liver.All mammalian cells contains cell surface transferrin receptors that bind with ferrotransferrin with high affinity.

The transferrin dimer carrying two bound atoms of Fe³⁺ called ferrotransferrin binds to the transferrin receptor at the cell surface