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Description
Human CD21, His tagProduct Specification Species Human Synonyms Complement receptor type 2, Cr2, Complement C3d receptor, Epstein Barr virus receptor (EBV receptor) Accession P20023 Amino Acid Sequence Protein sequence(P20023, Ile21 Arg971, with C 10*His)
Product Specification
| Species | Human |
| Synonyms | Complement receptor type 2, Cr2, Complement C3d receptor, Epstein-Barr virus receptor (EBV receptor) |
| Accession | P20023 |
| Amino Acid Sequence | Protein sequence(P20023, Ile21-Arg971, with C-10*His) ISCGSPPPILNGRISYYSTPIAVGTVIRYSCSGTFRLIGEKSLLCITKDKVDGTWDKPAPKCEYFNKYSSCPEPIVPGGYKIRGSTPYRHGDSVTFACKTNFSMNGNKSVWCQANNMWGPTRLPTCVSVFPLECPALPMIHNGHHTSENVGSIAPGLSVTYSCESGYLLVGEKIINCLSSGKWSAVPPTCEEARCKSLGRFPNGKVKEPPILRVGVTANFFCDEGYRLQGPPSSRCVIAGQGVAWTKMPVCEEIFCPSPPPILNGRHIGNSLANVSYGSIVTYTCDPDPEEGVNFILIGESTLRCTVDSQKTGTWSGPAPRCELSTSAVQCPHPQILRGRMVSGQKDRYTYNDTVIFACMFGFTLKGSKQIRCNAQGTWEPSAPVCEKECQAPPNILNGQKEDRHMVRFDPGTSIKYSCNPGYVLVGEESIQCTSEGVWTPPVPQCKVAACEATGRQLLTKPQHQFVRPDVNSSCGEGYKLSGSVYQECQGTIPWFMEIRLCKEITCPPPPVIYNGAHTGSSLEDFPYGTTVTYTCNPGPERGVEFSLIGESTIRCTSNDQERGTWSGPAPLCKLSLLAVQCSHVHIANGYKISGKEAPYFYNDTVTFKCYSGFTLKGSSQIRCKADNTWDPEIPVCEKETCQHVRQSLQELPAGSRVELVNTSCQDGYQLTGHAYQMCQDAENGIWFKKIPLCKVIHCHPPPVIVNGKHTGMMAENFLYGNEVSYECDQGFYLLGEKKLQCRSDSKGHGSWSGPSPQCLRSPPVTRCPNPEVKHGYKLNKTHSAYSHNDIVYVDCNPGFIMNGSRVIRCHTDNTWVPGVPTCIKKAFIGCPPPPKTPNGNHTGGNIARFSPGMSILYSCDQGYLLVGEALLLCTHEGTWSQPAPHCKEVNCSSPADMDGIQKGLEPRKMYQYGAVVTLECEDGYMLEGSPQSQCQSDHQWNPPLAVCRSRGGGGSHHHHHHHHHH |
| Expression System | HEK293 |
| Molecular Weight | Theoretical:105.8kDa Actual:125kDa |
| Purity | ＞95% by SDS-PAGE |
| Endotoxin | <1EU/μg |
| Tag | with C-10*His |
| Physical Appearance | Lyophilized Powder |
| Storage Buffer | Lyophilized from a 0.2 μm filtered solution of 0.2M PBS, 1mM EDTA, pH7.4. |
| Reconstitution | Reconstitute no more than 1 mg/mL according to the size in deionized water after rapid centrifugation. |
| Stability & Storage | 12 months from date of receipt, -20 to -70 °C as supplied. 6 months, -20 to -70 °C under sterile conditions after reconstitution. 1 week, 2 to 8 °C under sterile conditions after reconstitution. Please avoid repeated freeze-thaw cycles. |
Background
Complement receptor type 2 (CR2), also known as complement C3d receptor, Epstein-Barr virus receptor, and CD21 (cluster of differentiation 21), is a protein that in humans is encoded by the CR2 gene. CR2 is involved in the complement system. It binds to iC3b (inactive derivative of C3b), C3dg, or C3d. B cells express CR2 receptors on their surfaces, allowing the complement system to play a role in B-cell activation and maturation. Complement receptor 2 interacts with CD19, and, on mature B cells, forms a complex with CD81 (TAPA-1). The CR2-CD19-CD81 complex is often called the B cell co-receptor complex, because CR2 binds to opsonized antigens through attached C3d (or iC3b or C3dg) when the B-cell receptor binds antigen. This results in the B cell having greatly enhanced response to the antigen.
Shipping Notes
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Exchange/Return Notes
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4.1 ★★★★★
Based on 1488 reviews
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Product Reviews
★★★★★ 5
Survived my dog… which almost nothing does!
Size: Medium, Color: Watermelon, Size: Medium, Color: Watermelon
I have a pit mix who is an expert-level destroyer of squeaky toys. Most “durable” toys last her maybe 5–15 minutes before the squeaker is gone.
This one lasted a full HOUR of play (constant squeaking, chewing, and trying to find a weak spot) and she still didn’t manage to break it. That’s honestly unheard of for her.
What I like:
The flat shape makes it hard for her to get a good “kill grip”
The squeaker isn’t easy to isolate and destroy
It keeps her engaged instead of just ripping it open immediately
She actually spent a lot of time just booping it with her nose to make it squeak, which she loves.
I ended up putting it away before she could eventually destroy it, and I’ll be rotating it to make it last longer. It’s now a high-value toy in our house.
If you have a dog that destroys every squeaky toy in minutes, this is absolutely worth trying. I’m already planning to buy more from this line.
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Reviewed in the United States on April 6, 2026
★★★★★ 3
Not for aggressive chewers
Size: Medium, Color: Carrot
This product is pretty strong, but my dog tore it apart in 5 minutes. The size is great, and my dog loved tearing it apart. I wish it lasted longer.
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Reviewed in the United States on May 6, 2026
★★★★★ 4
Good!!!
Size: Medium, Color: Avocado
Excellent quality and durability.My pets really enjoy it and it's almost impossible to damage it!!
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Reviewed in the United States on May 31, 2026
★★★★★ 5
Recommended by my chihuahua puppy!
Size: Small, Color: Waffle, Size: Small, Color: Waffle
This has been a fantastic toy for my chihuahua puppy. She actually carries it around by the tag and loves rolling it over with her nose. It's a little big for her, but she still really enjoys it.
The tough edges are perfect for her little tiny shark teeth. I think she'll like this one even more as she begins teething.
It's obviously an adorable toy and it has held up really well so far. It does have a loud squeaker if that's something your dog likes or dislikes. Mine doesn't have the jaw strength or size to squeak it, but she likes it when I do it.
Considering what I paid and the many low quality toys on the market, this thing is a great value. Highly recommend it for toy and small breed dogs and puppies!
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Reviewed in the United States on June 9, 2026
★★★★★ 5
Tough Versatile Interactive & Chew Toy
Size: Medium, Color: Strawberry
Update: the Snake is the absolute best in terms of entertainment value. Provides tugging opportunities and our dog is obsessed with it. Love these toys.
This is quite literally one of the only toys we can leave with our puppy as both an interactive and self-play chew toy. Our small puppy (<20lbs) destroys every plush and latex toy in minutes. Has no interest in playing alone with durable toys like Kong and gets bored of them if we don’t play with them interactively. This satisfies our dog’s needs to chew on toys and keeps her entertained when we want a break but also quickly becomes a beloved interactive toy we can play fetch with. Yes, eventually our doggo destroys it as expected since we are using to both as a chew and interactive toy but it takes quite a while and we are very satisfied and impressed. This one stands the test of time.
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Reviewed in the United States on May 8, 2026