From Proteopediaproteopedia link
Extracellular domain of the LDL receptor
[LDLR_HUMAN] Defects in LDLR are the cause of familial hypercholesterolemia (FH) [MIM:143890]; a common autosomal semi-dominant disease that affects about 1 in 500 individuals. The receptor defect impairs the catabolism of LDL, and the resultant elevation in plasma LDL-cholesterol promotes deposition of cholesterol in the skin (xanthelasma), tendons (xanthomas), and coronary arteries (atherosclerosis).                               [:]           
[LDLR_HUMAN] Binds LDL, the major cholesterol-carrying lipoprotein of plasma, and transports it into cells by endocytosis. In order to be internalized, the receptor-ligand complexes must first cluster into clathrin-coated pits. In case of HIV-1 infection, functions as a receptor for extracellular Tat in neurons, mediating its internalization in uninfected cells.
Publication Abstract from PubMed
The low-density lipoprotein receptor mediates cholesterol homeostasis through endocytosis of lipoproteins. It discharges its ligand in the endosome at pH < 6. In the crystal structure at pH = 5.3, the ligand-binding domain (modules R2 to R7) folds back as an arc over the epidermal growth factor precursor homology domain (the modules A, B, beta propeller, and C). The modules R4 and R5, which are critical for lipoprotein binding, associate with the beta propeller via their calcium-binding loop. We propose a mechanism for lipoprotein release in the endosome whereby the beta propeller functions as an alternate substrate for the ligand-binding domain, binding in a calcium-dependent way and promoting lipoprotein release.
Structure of the LDL receptor extracellular domain at endosomal pH.,Rudenko G, Henry L, Henderson K, Ichtchenko K, Brown MS, Goldstein JL, Deisenhofer J Science. 2002 Dec 20;298(5602):2353-8. Epub 2002 Nov 29. PMID:12459547
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.