Q. Define Low - density lipoprotein?
Ans.
LDL is the major cholesterol-rich lipoprotein carrying approximately 70 per cent of plasma cholesterol. It serves to transport cholesterol to peripheral cells.
The Nobel laureates Brown and Goldstein identified the LDL receptor that recognizes apoprotein B100 of LDL particles (Brown and Goldstein, 1986). The receptors are large glycoproteins situated on the surface of cells in specialized areas termed coated pits. Coated pits are organelles necessary for the internalization of macromolecules. The LDL receptor gene has been cloned and localized to the short arm of chromosome 19.
The clinical relevance of this structural detail of the receptor will be appreciated when the inborn error of cholesterol metabolism called familial hypercholesterolaemia is discussed. In this condition there are defects in the gene coding for the receptor.