Clumping factor A

Clumping factor A is a major virulence factor and a protein from Staphylococcus aureus.  It plays a role in several types of infections, such as infective endocarditis, septic arthritis, kidney abscesses, and sepsis/septicemia. ClfA binds to the fibrinogen protein in blood plasma, allowing the bacteria to stick to platelets and begin creating blood clots(thrombus). ClfA binding to fibrinogen is essential in thrombus formation. Fibrinogen is a protein that is made of three pairs of non identical polypeptide chains. It is then broken down by thrombin during blood coagulation, which releases a fibrin monomer. These monomers combine to make a network that gives tensile strength to a blood clot. These fibrin clots are the substrate of the fibrinolytic system.

ClfA also has been shown to bind to complement regulator I protein.