New insights into the structure and function of the plasminogen/plasmin system

Plasminogen is the zymogen form of plasmin, an enzyme that plays a fundamental role in the dissolution of fibrin clots, the extracellular matrix and other key proteins involved in immunity and tissue repair. Comprising seven distinct domains (an N-terminal Pan-apple domain (PAp), 5 kringle domains (KR) and the serine protease domain (SP)), plasminogen undergoes a complex, incompletely understood conformational change that is key to its activation. Here, we review our current understanding of the structural basis for plasminogen activation with regard to new insights derived from crystallographic and biochemical studies.