• Purity

  >95%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining.

• Endotoxin Level

  <0.10 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured in a competitive binding assay. When human LDL is immobilized at 1 μg/mL (100 μL/well), Recombinant Human LDL R inhibits 50% binding of Biotinylated Recombinant Human LDL R (0.5 μg/mL) at the concentration range of 0.2-1.2 μg/mL.

• Source

  Human embryonic kidney cell, HEK293-derived Ala22-Arg788 (Asp193Ala), with a C-terminal 6-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Ala22

• Predicted Molecular Mass

  86 kDa

• SDS-PAGE

  120-140 kDa, reducing conditions

Data Images

Background: LDL R

The low density lipoprotein receptor (LDL R) is the founding member of the LDL R family of widely expressed cell surface scavenger receptors (1-5). Members of the family are endocytic receptors, but can also co-regulate adjacent cell-surface signaling molecules (3, 4). Many proteins in the LDL R family are cleaved by extracellular proteases to release soluble forms to the circulation, and many of these soluble forms are active (1, 6). Mature LDL R is a 120-160 kDa (depending on glycosylation) type I transmembrane glycoprotein that contains cysteine-rich complement-like repeats (class A LDL domains), calcium-binding EGF repeats, and  
beta -propeller structures (class B LDL repeats) in the extracellular domain (ECD) (1-7). A membrane-proximal Ser/Thr-rich region shows extensive O-linked glycosylation (4, 8). A cytoplasmic NPxY motif links the LDL R to clathrin pits for endocytosis, and binds to select adaptor proteins (1, 4, 8). The human LDL R ECD shares 78%, 76%, 81% and 82% aa sequence identity with mouse, rat, bovine, and porcine LDL R, respectively. LDL R is constitutively and widely expressed. Its class A LDL domains near the N-terminus bind apoB and apoE, the apolipoproteins of low- and very low-density lipoproteins (LDL and VLDL), respectively (1, 2, 4, 9). Hepatocyte LDL R is responsible for endocytosis and clearing of most plasma LDL cholesterol (2, 9). At the low pH of the endocytic vesicle, it dissociates, allowing degradation of LDL and recycling of LDL R to the cell surface (1, 4).  Lack of LDL R expression or function causes familial hypercholesterolemia (FH) (4, 9, 10). The protease PCSK9 (proprotein convertase subtilisin/kexin type 9) can also cause increased plasma cholesterol by promoting LDL R degradation rather than recycling to the cell surface (10-12). Soluble forms of approximately 140 kDa and 28 kDa are reported to be released by phorbol esters or interferons, respectively (6, 7).

• References:

1. Go, G.W. and A. Mani (2012) Yale J. Biol. Med. 85:19.

2. Ren, G. et al. (2010) Proc. Natl. Acad. Sci. USA 107:1059.

3. Bujo, H. and Y. Saito (2006) Arterioscler. Thromb. Vasc. Biol. 26:1246.

4. Gent, J. and I. Braakman (2004) Cell. Mol. Life Sci. 61:2461.

5. Yamamoto, T. et al. (1984) Cell 39:27.

6. Begg, M.J. et al. (2004) Eur. J. Biochem. 271:524.

7. Fischer, D.G. et al. (1993) Science 262:250.

8. Stolt, P.C. and H.H. Bock (2006) Cell. Signal. 18:1560.

9. Defesche, J.C. (2004) Semin. Vasc. Med. 4:5.

10. De Castro-Oros, I. et al. (2010) Appl. Clin Genet. 3:53.

11. Zhang, D.W. et al. (2008) Proc. Natl. Acad. Sci. USA 105:13045.

12. Tavori, H. et al. (2013) Circulation 127:2403.

• Long Name:

  Low Density Lipoprotein Receptor

• Entrez Gene IDs:

  3949 (Human); 16835 (Mouse); 300438 (Rat)

• Alternate Names:

  FH; FHC; LDL R; LDL receptor; LDLCQ2; LDLR; low density lipoprotein receptor; low-density lipoprotein receptor class A domain-containing protein 3; low-density lipoprotein receptor