C4b Protein

Purified human C4b protein

Store at -70°C or below. Avoid freeze/thaw.

Frozen liquid. 10 mM sodium phosphate, 145 mM NaCl, pH 7.3. No preservative, 0.22 µm filtered.

C4b is derived from native C4 upon cleavage and release of C4a. It is prepared by cleavage of purified C4 with the classical pathway activated protease C1s enzyme (#A104). Native human C4b is a glycosylated (~7.3%) polypeptide containing three disulfide-linked chains. C4b is central to the function of two of the three pathways of complement. Both the classical and lectin pathways of complement activation generate surface-bound active proteases that cleave C4 (C1s in the classical pathway and MASP1/2 in the lectin pathway). These enzymes cleave a peptide bond in C4 releasing the anaphylatoxin C4a and activating C4b. For a fraction of a second after proteolytic activation C4b can covalently attach to the surface of the target.