Human fibrinogen possesses binding site for staphylococci on Aα and Bβ polypeptide chains

Abstract

THE fibrinogen molecule, which comprises 5% of plasma proteins, is involved in enzymatic reactions responsible for formation and dissolution of the fibrin clot¹. Thereby, fibrinogen is being transformed by thrombin into fibrin, which is cross linked by glutaminyltransamidase (factor XIII), and ultimately degraded by plasmin. The Aα, Bβ and γ polypeptide chains (nomenclature according to the recommendations of the Committee on Nomenclature of the International Society on Thrombosis and Haemostasis, 1971) of fibrinogen involved in these reactions and the sites of enzymatic attack thereon are defined^2–8. In addition to being involved in the enzymatic reactions responsible for formation and dissolution of the fibrin clot, fibrinogen exhibits the ability to interact in a non-enzymatic reaction with pathogenic staphylococci to cause their clumping⁹. Clumping of staphylococci is used to detect fibrinogen and its derivatives in blood and body fluids^10,11. This reaction can detect as little as 0.03 µg human fibrinogen or its derivatives. The mechanism through which human fibrinogen interacts with staphylococci is however, unexplained and the localisation of the binding site(s) for staphylococci remains unknown. We therefore studied localisation of the binding site for staphylococci on human fibrinogen. We now report that the binding site for staphylococci is located on Aα and Bβ chains of human fibrinogen.