It inhibits the action the classical and the lectin pathways, more specifically
C4. It also has ability to bind C3b. C4BP accelerates decay of
C3-convertase and is a cofactor for serine protease factor I which cleaves C4b and C3b. C4BP binds apoptotic and necrotic cells as well as DNA, to clean up after injury. The interaction with apoptotic and necrotic cells is mediated by the
Gla domain of protein S and does not affect the ability of C4BP to inhibit complement. A number of bacterial and fungal pathogens capture human C4BP and use it to prevent binding of C4b, which allows them to establish infection. No full deficiency of C4BP has been found yet. C4BP interacts also with
heparin,
C-reactive protein (CRP),
serum amyloid P component (SAP),
fibromodulin,
osteoadherin,
chondroadherin, proline arginine-rich end leucine-rich repeat protein (
PRELP),
streptococcal M-proteins,
gonococcal porins, Outer membrane protein A from
E. coli, Ubiquitous surface protein 1 and 2 from
Moraxella. == References ==