STRUCTURE AND PROPERTIES OF EXTRACELLULAR PROTEINS REGULATING THE PROTEOLYTIC PHASE OF COMPLEMENT ACTIVATION

The structure and biochemical properties of the most important fluid-p hase regulatory proteins of complement including Cl-inhibitor, factors I, H, J, properdin, and C4b-binding protein are reviewed. Three types of proteolytic complement cascade regulation by the proteins are summ arized. The first is an inhibition of complement proteinases, the seco nd is based on proteolytic degradation of complement activation produc ts, and the third includes the regulation of stability of complement p rotein complexes. The main functional role of fluid-phase regulatory p roteins is the limitation of the proteolytic cascade.