C-Reactive Protein

C-reactive protein (CRP) is a member of the pentraxin family of proteins that are characterized by a cyclic pentameric structure. Human CRP gene encodes a 224 amino acids precursor. The mature human CRP protein has 206 amino acids that are noncovalently linked to form the pentameter. Human CRP shares 71% and 64% amino acid sequence homology with mouse and rat respectively. CRP, synthesized by hepatocytes, is a major acute phase serum protein in human. IL6, IL1 and glucocorticoids are the major inducer of the CRP gene. The physiological role of CRP is to bind to phosphocholine expressed on the surface of dead or dying cells (and some types of bacteria) in order to activate the complement system. CRP binds to phosphocholine on microbes and damaged cells and enhances phagocytosis by macrophages. Thus, CRP participates in the clearance of necrotic and apoptotic cells. CRP rises up to 50,000-fold in acute inflammation, such as infection. It rises above normal limits within 6 hours, and peaks at 48 hours. Its half-life is constant, and therefore its level is mainly determined by the rate of production. It has been shown that high levels of CRP in humans is associated with an increased risk of cardiovascular diseases.