Structure of the ternary microplasmin-staphylokinase-microplasmin complex: a proteinase-cofactor-substrate complex in action
[PLMN_HUMAN] Defects in PLG are the cause of plasminogen deficiency (PLGD) [MIM:217090]. PLGD is characterized by decreased serum plasminogen activity. Two forms of the disorder are distinguished: type 1 deficiency is additionally characterized by decreased plasminogen antigen levels and clinical symptoms, whereas type 2 deficiency, also known as dysplasminogenemia, is characterized by normal, or slightly reduced antigen levels, and absence of clinical manifestations. Plasminogen deficiency type 1 results in markedly impaired extracellular fibrinolysis and chronic mucosal pseudomembranous lesions due to subepithelial fibrin deposition and inflammation. The most common clinical manifestation of type 1 deficiency is ligneous conjunctivitis in which pseudomembranes formation on the palpebral surfaces of the eye progresses to white, yellow-white, or red thick masses with a wood-like consistency that replace the normal mucosa.       
[PLMN_HUMAN] Plasmin dissolves the fibrin of blood clots and acts as a proteolytic factor in a variety of other processes including embryonic development, tissue remodeling, tumor invasion, and inflammation. In ovulation, weakens the walls of the Graafian follicle. It activates the urokinase-type plasminogen activator, collagenases and several complement zymogens, such as C1 and C5. Cleavage of fibronectin and laminin leads to cell detachment and apoptosis. Also cleaves fibrin, thrombospondin and von Willebrand factor. Its role in tissue remodeling and tumor invasion may be modulated by CSPG4. Binds to cells. Angiostatin is an angiogenesis inhibitor that blocks neovascularization and growth of experimental primary and metastatic tumors in vivo. [SAK_BPP42] Potent plasminogen activator that converts plasminogen into plasmin. It forms a 1:1 complex with plasmin, which in turn activates other plasminogen molecules.
Publication Abstract from PubMed
The serine proteinase plasmin is the key fibrinolytic enzyme that dissolves blood clots and also promotes cell migration and tissue remodeling. Here, we report the 2.65 A crystal structure of a ternary complex of microplasmin-staphylokinase bound to a second microplasmin. The staphylokinase 'cofactor' does not affect the active-site geometry of the plasmin 'enzyme', but instead modifies its subsite specificity by providing additional docking sites for enhanced presentation of the plasminogen 'substrate' to the 'enzymes's' active site. The activation loop of the plasmin 'substrate', cleaved in these crystals, can be reconstructed to show how it runs across the active site of the plasmin 'enzyme' prior to activation cleavage. This is the first experimental structure of a productive proteinase-cofactor-macromolecular substrate complex. Furthermore, it provides a template for the design of improved plasminogen activators and plasmin inhibitors with considerable therapeutical potential.
The ternary microplasmin-staphylokinase-microplasmin complex is a proteinase-cofactor-substrate complex in action.,Parry MA, Fernandez-Catalan C, Bergner A, Huber R, Hopfner KP, Schlott B, Guhrs KH, Bode W Nat Struct Biol. 1998 Oct;5(10):917-23. PMID:9783753
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.