SC5b-9 Protein

Vitronectin (S Protein) binds to membrane attack complexes that fail to insert into membranes. The result is a soluble complex of S Protein and C5b-9 and this has been named SC5b-9. Activation of complement in the absence of bilipid layer membranes results in most of the activated C5 forming SC5b-9 complexes. This can occur with activating particles such as immune complexes, yeast and bacterial cell walls. The SC5b-9 complexes can have more than one C9 (usually three) and more than one S Protein (usually three) per complex.