Immune · Complement-derived anaphylatoxin peptide
Complement C3a
Also known as C3a; C3 anaphylatoxin
A 77-residue human complement fragment whose intact C-terminal arginine supports signalling through C3aR1.
- Length
- 77 amino acids in the mature human reference sequence
- Half-life
- Not well characterised
- Mechanism
- C3a activates C3a receptor 1 (C3aR1), a G protein-coupled receptor that can initiate calcium mobilisation and downstream signalling. Removal of its C-terminal arginine by carboxypeptidases markedly reduces conventional C3aR1 agonist activity.
- Studied in
- C3a is investigated in receptor-expressing cell lines, primary immune-cell assays and animal models of complement-dependent cell recruitment and tissue signalling.
About Complement C3a
C3a is released from the N-terminal region of the C3 alpha chain when C3 convertases cleave complement component C3. The mature human fragment contains 77 amino acids and three intramolecular disulphide bonds that stabilise its compact, predominantly helical structure. Historical biochemical studies identified C3a as one of the soluble anaphylatoxin fragments generated during complement activation. Its sequence, molecular mass and processing state should be specified for each research preparation.
The principal established receptor is C3aR1, although cellular responses depend on receptor abundance and the surrounding signalling environment. Laboratory endpoints include calcium flux, receptor internalisation, mediator release and cell migration in appropriately responsive systems. The terminal arginine is especially important for conventional receptor activation; enzymatic removal produces C3a-desArg, a distinct analyte. Because sample processing can change the balance between these forms, immunoreactivity alone does not necessarily establish intact, biologically active C3a.
Laboratory notes
- Confirm species, sequence, disulphide status and any recombinant tags or terminal extensions.
- Use validated sample handling to minimise ex vivo complement activation and carboxypeptidase-mediated conversion.
- Check antibody cross-reactivity with C3, C3 fragments and C3a-desArg; assess endotoxin when studying immune-cell responses.
Storage and reconstitution basics: storage guide.
Questions about Complement C3a
Is C3a the same molecule as C3a-desArg?
No. C3a-desArg lacks the terminal arginine, a change that markedly reduces conventional signalling through C3aR1.
Why does the entry specify a human reference length?
The 77-residue length describes mature human C3a. Species origin and recombinant construct design must be checked separately.
Does an immunoassay establish C3a receptor activity?
Not by itself. Antibody recognition can persist after processing or structural changes; a receptor-based functional assay provides complementary information.
Is Complement C3a for human use?
No. It is supplied strictly for in-vitro laboratory research and is not for human or animal consumption.
Related research peptides
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