Streptokinase–plasminogen protein–protein interface (SK-Pg interface)

The streptokinase–plasminogen protein–protein interface is a critical molecular interaction used in thrombolytic therapy to dissolve blood clots (StatPearls, 2023). Streptokinase, a non-enzymatic protein from beta-hemolytic streptococci, binds to human plasminogen in a 1:1 stoichiometric ratio to form an activator complex (PubMed: 12631490). This binding induces a conformational change in plasminogen, exposing its active site and allowing the complex to catalytically convert other plasminogen molecules into plasmin (UniProt: P00747). Plasmin then degrades the fibrin matrix of thrombi, restoring blood flow in conditions like acute myocardial infarction and pulmonary embolism (NIH: NBK553141). Because streptokinase is a foreign bacterial protein, the interface is associated with high immunogenicity and the risk of systemic fibrinolysis, leading to potential bleeding complications (PubMed: 17556633). This target is unique because it involves the allosteric activation of a human zymogen by a bacterial cofactor rather than direct enzymatic cleavage.

Other names

Streptokinase-plasminogen complexSK-Pg complexStreptokinase-plasmin activator complexAPSAC interface

Streptokinase binds to plasminogen to form a 1:1 stoichiometric complex, inducing a conformational change that exposes an active site on plasminogen; this complex then enzymatically cleaves free plasminogen into active plasmin (StatPearls, 2023; PubMed: 12631490).