• Purity

  >95%, by SDS-PAGE under reducing conditions and visualized by silver stain

• Endotoxin Level

  <1.0 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by its binding ability in a functional ELISA.

  When Recombinant Human (rh) CD55/DAF is coated at 1 μg/mL (100 μL/well), the concentration of rhCD97 that produces 50% of the optimal binding response is found to be approximately 0.5-2.5 μg/mL.

• Source

  Mouse myeloma cell line, NS0-derived

  Human CD55 (Asp35 - Ser353) Accession # P08174.4	DI	6-His tag
  N-terminus		C-terminus

• Accession #

• N-terminal Sequence    
  Analysis

  Asp35

• Predicted Molecular Mass

  36.0 kDa

• SDS-PAGE

  61-75 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: CD55/DAF

CD55, also known as DAF or decay-accelerating factor, is a 70 - 75 kDa member of the RCA family of proteins. Human RCA (regulators of complement/C’ activation) proteins are products of chromosome 1 genes that are ubiquitously expressed on cells exposed to plasma complement proteins (1 - 4). A hallmark of RCA proteins is the presence of four to 30 SCRs (short consensus repeats; also called CCPs for C’ control protein modules) in their plasma-exposed regions. SCRs are characterized by a 60 - 65 amino acid (aa) module that contains a highly conserved Trp residue and two internal disulfide bonds that create a beta -barrel structure (1). Human CD55 is synthesized as a 381 aa precursor that contains a 34 aa signal sequence, a 319 aa mature region and a 28 aa C‑terminal prosegment (5, 6). The mature region contains four SCR modules and a C‑terminal O‑glycosylated extension (7). Following cleavage of the prosegment, a serine is exposed that serves as an anchor for a GPI-linkage (8). Multiple polymorphisms are found in the molecule. Alternate splicing also exists. One form that may not be translated shows an intron insertion in the prosegment, resulting in a 79 aa substitution for the standard C‑terminal 20 aas of the prosegment (6). Another form generates a truncated 199 aa precursor that cannot be membrane-bound and may not be secreted (9). Mature CD55 is 53% and 84% aa identical to mouse and monkey CD55, respectively. CD55 is known to bind CD97 via the first SCR (4). It also binds physiologically-generated C3 convertases with its second and third SCRs (7, 10). Binding results in an accelerated “decay”, or dissociation of active C3 convertases, thus blocking the development of C’ attack complexes on nonforeign cells (1, 2). Finally, viruses and bacteria are also known to utilize multiple SCR sites for infection (4).

• References:

1. Herbert, A. et al. (2002) Biochem. Soc. Trans. 30:990.

2. Miwa, T. and W-C. Song (2001) Int. Immunopharmacol. 1:445. 

3. Hourcade, D. et al. (2000) Immunopharmacology 49:103. 

4. Lea, S. (2002) Biochem. Soc. Trans. 30:1014. 

5. Medof, M.E. et al. (1987) Proc. Natl. Acad. Sci. USA 84:2007. 

6. Caras, I.W. et al. (1987) Nature 325:545.

7. Lukacik, P. et al. (2004) Proc. Natl. Acad. Sci. USA 101:1279.

8. Moran, P. et al. (1991) J. Biol. Chem. 266:1250.

9. Lublin, D.M. et al. (1994) Blood 84:1276.

10. Williams, P. et al. (2003) J. Biol. Chem. 278:10691.

• Entrez Gene IDs:

  1604 (Human); 13136 (Mouse)

• Alternate Names:

  CD55 antigen; CD55 molecule, decay accelerating factor for complement (Cromer blood group); CD55; CR; CRdecay accelerating factor for complement (CD55, Cromer blood group system); CROMDAFcomplement decay-accelerating factor; DAF; decay accelerating factor for complement; TC