Immune · Disulphide-cyclised complement-binding peptide
Compstatin
Also known as Original compstatin; cyclic C3-binding peptide
A cyclic 13-residue C3-binding peptide used to investigate complement activation in species-compatible laboratory systems.
- Length
- 13 amino acids
- Half-life
- Not well characterised
- Mechanism
- Compstatin binds complement component C3 and its activated fragment C3b at a site associated with the MG4–MG5 domains. Binding inhibits convertase-mediated C3 cleavage, limiting downstream complement activation without directly targeting a cell-surface receptor.
- Studied in
- Purified complement systems, human and non-human primate serum assays, and complement-exposed cell cultures are used to investigate C3-dependent cascade activation.
About Compstatin
Compstatin was identified in 1996 through screening a phage-displayed peptide library for binding to complement component C3. The original sequence is ICVVQDWGHHRCT, with a disulphide bond connecting cysteines at positions 2 and 12. This linkage creates an 11-residue ring flanked by terminal residues. The name now also appears in descriptions of an extensive analogue family, so sequence, terminal modifications and cyclisation chemistry are essential identifiers when selecting material or comparing published experiments.
Unlike inhibitors directed at individual initiating pathways, compstatin acts at C3, a shared component of the classical, lectin and alternative complement pathways. Its activity is strongly species-dependent: the original peptide recognises human and selected non-human primate C3 but is generally unsuitable for conventional mouse or rat complement assays. Structural and biochemical studies examine binding at the C3 MG4–MG5 region, inhibition of C3 processing, and consequent changes in complement deposition on experimental surfaces.
Laboratory notes
- Verify the Cys2–Cys12 disulphide and terminal chemistry; linear, reduced or chemically modified material is not equivalent to the original cyclic peptide.
- Confirm C3 species compatibility before choosing serum or animal-derived assay components.
- Standardise serum handling, freeze–thaw history and divalent-cation conditions, since these independently affect complement activity.
Storage and reconstitution basics: storage guide.
Questions about Compstatin
Can original compstatin be evaluated in ordinary mouse serum?
Mouse C3 is generally not susceptible to the original peptide. A negative result in mouse serum therefore does not establish that the peptide is inactive in a compatible system.
Is compstatin a receptor antagonist?
No. Its direct target is the soluble complement protein C3 and related C3b, rather than a conventional cell-surface receptor.
Are all compstatin analogues equivalent?
No. Sequence substitutions, terminal modifications and conjugation can substantially alter affinity, solubility and stability. Each analogue requires its own identity and assay documentation.
Is Compstatin for human use?
No. It is supplied strictly for in-vitro laboratory research and is not for human or animal consumption.
Related research peptides
All products are sold for laboratory research use only. Not for human consumption, not a medicine, not for diagnosing, treating or preventing any condition.