Acts as a complement inhibitor by disrupting the formation of the classical C3 convertase. Isoform 3 inhibits the classical complement pathway, while membrane-bound isoform 1 inhibits deposition of C3b via both the classical and alternative complement pathways.
Subcellular locations: Membrane
Subcellular locations: Secreted
Isoform 3 is the predominant isoform in all tissues except cortex, cerebellum, kidney, and breast. Isoform 1 is found primarily in the esophagus and the brain.