• Purity

  >90%, by SDS-PAGE under reducing conditions and visualized by silver stain.

• Endotoxin Level

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

• Activity

  Measured by its ability to bind immobilized human LDL in a functional ELISA.

• Source

  Mouse myeloma cell line, NS0-derived Ala22-Arg790 (Ala23Val and Cys27Gly), with a C-terminal 10-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Ala22

• Predicted Molecular Mass

  85.7 kDa

• SDS-PAGE

  130-135 kDa, reducing conditions

Carrier Free

What does CF mean?

CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.

What formulation is right for me?

In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.

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 mouse LDL R ECD shares 78%, 86%, 76% and 76% aa sequence identity with human, 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. Polvino, W.J. et al. (1992) Somat. Cell Mol. Genet. 18:443.

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