LDL Receptor

1. The low density lipoprotein receptor is a cell surface receptor that plays an important role in cholesterol homeostasis.
2. The low density lipoprotein receptor is synthesized as a 120-kD glycoprotein precursor that undergoes change to a 160-kD mature glycoprotein through the covalent addition of a 40-kD protein. 
3. The human LDL receptor is an 839-amino acid protein rich in cysteine, with multiple copies of the Alu family of repetitive DNAs. 
4. The LDL receptor shares DNA sequence homology with the epidermal growth factor (EGF) receptor. 
5. The LDL receptor gene (LDLR) was mapped to chromosome 19. 
6. The LDLR was regionalized to 19p13.1-p13.3 by in situ hybridization. 
7. LDL bound to cultured fibroblasts in a manner consistent with a receptor. 
8. LDL binding resulted in suppression of cholesterol synthesis by the cell via repression of HMG CoA reductase.
9. LDL bound at the cell membrane and were taken into the cell ending up in lysosomes where the protein was degraded.
10. After internalization and degradation, the cholesterol was made available for repression of microsomal enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, the rate-limiting step in cholesterol synthesis.

More on mutations of the LDLR gene at http://omim.org/entry/606945