• Purity

  >80%, 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 the ability of the immobilized protein to support the adhesion of human red blood cells. Kelm, S.     et al. (1994) Current Biology     4:965. The ED    ₅₀ for this effect is 0.6‑3 µg/mL.

• Source

  Mouse myeloma cell line, NS0-derived Ser20-Gln1641, with a C-terminal 6-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Ser20

• Predicted Molecular Mass

  173.9 kDa

• SDS-PAGE

  175 kDa - 190 kDa, reducing conditions

Background: Siglec-1/CD169

Siglecs are sialic acid specific I-type lectins that belong to the immunoglobulin superfamily. Structurally, they are transmembrane proteins with an N-terminal Ig-like V-set domain followed by varying numbers of Ig-like C2-set domains (1, 2). Human Siglec-1, also known as sialoadhesin and CD169, is a 175 - 185 kDa glycoprotein. It contains a 1622 amino acid (aa) extracellular domain (ECD) with one Ig-like V-set domain and 16 Ig-like C2-set domains, a 21 aa transmembrane segment, and a 44 aa cytoplasmic domain (3). Within the ECD, human Siglec-1 shares approximately 70% aa sequence identity with mouse and rat Siglec-1. Alternate splicing generates a potentially soluble form of the ECD, and a second isoform with a substituted cytoplasmic domain. Siglec-1 expression is restricted to lymph node and splenic macrophages, plus some tissue macrophages (3). The adhesive function of Siglec-1 is supported by the N-terminal Ig-like domain which shows a selectivity for alpha 2,3-linked sialic acid residues (3 - 5). Siglec-1 binds a number of sialylated molecules including the mannose receptor, MGL1, MUC1, PSGL-1, and different glycoforms of CD43 (6 - 9). Its binding capacity can be masked by endogenous sialylated molecules (10, 11). The sialylated and sulfated N-linked carbohydrates that modify Siglec-1 itself are required for ligand binding (6, 7). Siglec-1 is expressed on dendritic cells following rhinovirus exposure, and these DC promote T cell anergy (12). It is also induced on circulating monocytes during systemic sclerosis and HIV-1 infection (13 - 15). Siglec-1 can trap HIV-1 particles for trans infection of permissive cells (14).

• References:

1. Varki, A. and T. Angata (2006) Glycobiology 16:1R.

2. Crocker, P.R. et al. (2007) Nat. Rev. Immunol. 7:255.

3. Hartnell, A. et al. (2001) Blood 97:288.

4. Nath, D. et al. (1995) J. Biol. Chem. 270:26184.

5. Crocker, P.R. et al. (1991) EMBO J. 10:1661.

6. Martinez-Pomares, L. et al. (1999) J. Biol. Chem. 274:35211.

7. Kumamoto, Y. et al. (2004) J. Biol. Chem. 279:49274.

8. Nath, D. et al. (1999) Immunology 98:213.

9. van den Berg, T.K. et al. (2001) J. Immunol. 166:3637.

10. Nakamura, K. et al. (2002) Glycobiology 12:209.

11. Barnes, Y.C. et al. (1999) Blood 93:1245.

12. Kirchberger, S. et al. (2005) J. Immunol. 175:1145.

13. York, M.R. et al. (2007) Arthritis Rheum. 56:1010.

14. Rempel, H. et al. (2008) PloS ONE 3:e1967.

15. van der Kuyl, A.C. et al. (2007) Plos ONE 2:e257.

• Long Name:

  Sialic Acid Binding Ig-like Lectin 1

• Entrez Gene IDs:

  6614 (Human); 20612 (Mouse); 311426 (Rat)

• Alternate Names:

  C19orf75; CD169; Siglec1; Siglec-1; SIGLECL1 SIGLEC family like 1