LDL receptor

Function

LDL (Low Density Lipoprotein) receptor (LDLR) mediates the endocytosis of cholesterol-rich LDL. LDLR recognizes the apoprotein B100 which is embedded in the outer layer of the LDL particle. LDLR sits on the cell surface and binds LDL particles which circulate in the blood stream. LDLR transports the LDL particle into the cell where the cholesterol is used. Upon release of the LDL particle, the LDLR is recycled back into the cell membrane surface^[1].

Disease

Mutations in LDLR which cause its lack of function are causing familial hypercholesterolemia^[2].

Structural highlights

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LDLR consists of a ligand-binding domain (LBD residues 1-292), epidermal growth factor precursor homology domain (EGFP residues 293-699), oligosaccharide-rich domain (residues 700-758), membrane-spanning domain (residues 759-781) and cytoplasmic domain (residues 782-832). LDLR LBD contains 7 ca. 40 amino acid long repeats ((LB1 residues 20-67; LB2 residues 55-104; LB3 residues 105-143; LB4 residues 144-196; LB5 residues 196-232; LB6 residues 234-272) containing 6 cysteine residues, making a calcium binding octahedral structure. LDLR EGFP contains 2 EGF repeats followed by 6 and another EGF repeat. LDLR LBD residues 133-273 are named C-type lectin-like domain.