Recombinant Human Siglec 3-Fc Chimera (carrier-free)

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Other Names
CD33, gp67
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750104 25 µg 148€
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750106 100 µg 372€
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Siglec proteins (sialic acid binding Ig-like lectins) are type I membrane proteins with an extracellular region containing a sialic acid binding V-set Ig-like domain at the N-terminus, followed by varying numbers of C2-set Ig domains. In the cytosolic domain, most Siglecs contain a combination of tyrosine motifs, including immunoreceptor tyrosine-based inhibitory motifs (ITIM), along with ITIM-like, Grb2-binding, and Fyn kinase sites. Siglecs are widely expressed on hematopoietic cells, often in a cell-type-specific manner. Their ligands, sialic acids, are negatively charged monosaccharides found on cell-surface glycoproteins and glycolipids. Studies suggest that Siglecs may participate in cell-cell interactions and act as receptors for the entry of viral or bacterial pathogens. In addition, the presence of ITIM indicates that these molecules play a role in the suppression of immunoreceptor signaling. Siglecs can be classified into two subgroups with Siglec 1, 2, and 4, as one group and a Siglec 3/CD33-related subgroup (Siglec 3 and 5 through 14) as the second. Siglec 3, also known as CD33 and GP67, is mainly expressed on myeloid cells and also on activated NK and T cells. Human Siglec 3 has two tyrosine residues in its cytoplasmic domain. When phosphorylated, these tyrosines could confer an inhibitory function. CD33 polymorphism has been associated with late-onset Alzheimer's disease.

Product Details
Technical Data Sheet (pdf)

Product Details

Human Siglec 3, amino acids (Asp18-His259) (Accession# NP_001763), was expressed in 293E cells with a C-terminal human IgG1 Fc tag.
Molecular Mass
This 493 amino acid recombinant protein has a predicted molecular mass of approximately 54.9 kD. The protein migrates approximately at 70 kD in DTT-reducing conditions and at 150 kD in non-reducing conditions by SDS-PAGE. The predicted N-terminal amino acid is Asp.
>95%, as determined by Coomassie stained SDS-PAGE.
0.22 µm filtered protein solution is in PBS, pH 7.2.
Endotoxin Level
Less than 0.1 EU per µg of protein as determined by the LAL method.
10 and 25 µg sizes are bottled at 200 µg/mL. 100 µg size and larger sizes are lot-specific and bottled at the concentration indicated on the vial (please contact technical support for concentration, or use our Lookup tool if you have a lot number.)
Please note, new lots of the 100 µg size will be lot-specific and may differ from previous lots that had a fixed concentration.
Storage & Handling
Unopened vial can be stored between 2°C and 8°C for up to 2 weeks, at -20°C for up to six months, or at -70°C or colder until the expiration date. For maximum results, quick spin vial prior to opening. The protein can be aliquoted and stored at -20°C or colder. Stock solutions can also be prepared at 50 - 100 µg/mL in appropriate sterile buffer, carrier protein such as 0.2 - 1% BSA or HSA can be added when preparing the stock solution. Aliquots can be stored between 2°C and 8°C for up to one week and stored at -20°C or colder for up to 3 months. Avoid repeated freeze/thaw cycles.
Recombinant human Siglec 3 is able to agglutinate human red blood cells with an ED50 = 0.5 - 4.0 µg/mL.


Application Notes

BioLegend carrier-free recombinant proteins provided in liquid format are shipped on blue-ice. Our comparison testing data indicates that when handled and stored as recommended, the liquid format has equal or better stability and shelf-life compared to commercially available lyophilized proteins after reconstitution. Our liquid proteins are validated in-house to maintain activity after shipping on blue ice and are backed by our 100% satisfaction guarantee. If you have any concerns, contact us at

Antigen Details

Human Siglec 3 is highly expressed on myeloid cells and activated NK and T cells, but is expressed poorly on B lymphocytes.
Siglec 3 recruits the tyrosine phosphatases SHP-1 and SHP-2 to its ITIMs. When cross-linked with FcgR1, Siglec 3 inhibits phosphorylation of tyrosine residues and the mobilization of calcium, suggesting that it may mediate inhibitory signals.
Red blood cells.
α2, 3- and α2, 6-linked disialic acid.
Cell Type
Hematopoietic stem and progenitors
Biology Area
Stem Cells
Molecular Family
Siglec Molecules
Antigen References

1. McMillan SJ, et al. 2013. Blood 121:2084.
2. Bax M, et al. 2010. Ann. Rheum. Dis. 69:42.
3. Angata T and Varki A. 2000. J. Biol. Chem. 275:22127.
4. Yu Z, et al. 2001. Biochem. J. 353:483.
5. Paul SP, et. al. 2000. Blood 96:483.
6. Hernandez-Caselles T, et al. 2006. J. Leukoc. Biol. 79:463.
7. Jiang T, et al. 2013. Mol. Neurobiol. 49:529.
8. Angata T. 2014. Glycobiology 24:785.

Gene ID
945 View all products for this Gene ID
View information about Siglec 3 on

Related FAQs

Does specific activity of a recombinant protein vary between lots?

Specific activity will vary for each lot and for the type of experiment that is done to validate it, but all passed lots will have activity within the established ED50 range for the product and we guarantee that our products will have lot-to-lot consistency. Please conduct an experiment-specific validation to find the optimal ED50 for your system.

Have your recombinants been tested for stability?

Our testing shows that the recombinant proteins are able to withstand room temperature for a week without losing activity. In addition the recombinant proteins were also found to withstand four cycles of freeze and thaw without losing activity.

How do you convert activity as an ED50 in ng/ml to a specific activity in Units/mg?
Use formula Specific activity (Units/mg) = 10e6/ ED50 (ng/mL)
How does the activity of your recombinant proteins compare to competitors?

We quality control each and every lot of recombinant protein. Not only do we check its bioactivity, but we also compare it against other commercially available recombinant proteins. We make sure each recombinant protein’s activity is at least as good as or better than the competition’s. In order to provide you with the best possible product, we ensure that our testing process is rigorous and thorough. If you’re curious and eager to make the switch to BioLegend recombinants, contact your sales representative today!

What is the specific activity or ED50 of my recombinant protein?

The specific activity range of the protein is indicated on the product datasheets. Because the exact activity values on a per unit basis can largely fluctuate depending on a number of factors, including the nature of the assay, cell density, age of cells/passage number, culture media used, and end user technique, the specific activity is best defined as a range and we guarantee the specific activity of all our lots will be within the range indicated on the datasheet. Please note this only applies to recombinants labeled for use in bioassays. ELISA standard recombinant proteins are not recommended for bioassay usage as they are not tested for these applications.

Go To Top Version: 1    Revision Date: 02-27-2015

For research use only. Not for diagnostic use. Not for resale. BioLegend will not be held responsible for patent infringement or other violations that may occur with the use of our products.


*These products may be covered by one or more Limited Use Label Licenses (see the BioLegend Catalog or our website, BioLegend products may not be transferred to third parties, resold, modified for resale, or used to manufacture commercial products, reverse engineer functionally similar materials, or to provide a service to third parties without written approval of BioLegend. By use of these products you accept the terms and conditions of all applicable Limited Use Label Licenses. Unless otherwise indicated, these products are for research use only and are not intended for human or animal diagnostic, therapeutic or commercial use.


BioLegend Inc., 8999 BioLegend Way, San Diego, CA 92121
Toll-Free Phone: 1-877-Bio-Legend (246-5343) Phone: (858) 768-5800 Fax: (877) 455-9587

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