Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A fragment corresponding to the intact dimeric form of the CH2 domain of rabbit IgG, including the hinge region disulfide linkage, was obtained by plasmin digestion of crystalline Fc derived from IgG by the action of papain. Identification and assessment of purity of the fragment was established by SDS-PAGE, amino acid composition analysis, N-terminus sequence and C-terminus amino acid analysis and SDS-urea-PAGE of the reduced fragment. The fragment retains serologic reactivity with anti-Fc specific antisera. Comparison of deglycosylation by endoglycosidase F indicates a more open special relationship between the two CH2 domains in the fragment than in Fc.
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PMID:Isolation and partial characterization of a fragment corresponding to the dimeric form of the CH2 domain of rabbit IgG. 309 28

Fully activable recombinant human plasminogen (rPlg) was expressed in mammalian cells employing either recombinant vaccinia virus or stable lines coexpressing alpha 2-plasmin inhibitor. A panel of eight variants of rPlg was constructed, in which progressively up to 6 basic amino acid residues in the hinge region of rPlg between the NH2-terminal acidic domain ("proactivation peptide") and kringle 1 were substituted by neutral residues. Analysis of the cleavage rates of these variants by plasmin revealed that the peptide bond at Arg68 is most susceptible, followed by Lys62 and Lys77. A variant with all 6 basic residues substituted was cleaved at Lys20. Three of these variants, PlgB (R68A, R70A), PlgF (R68A, R70A, K77H, K78H), and PlgG (R61A, K62A, R68A, R70A, K77H, K78H), as well as rPlg, were analyzed in more detail. The conformation of these plasminogens was analyzed by monitoring the change in intrinsic fluorescence upon binding of lysine analogs. This revealed that rPlg exhibits the native tight Glu1-plasminogen conformation, whereas PlgB, PlgF, and Plg G display an open conformation similar to Lys78-plasminogen, leading to an increased affinity for lysine analogs. This allowed a direct study of the impact of the activation-resistant conformation on the properties of Glu1-plasminogen. The open conformation of rPlg variants leads to an increased rate of activation by urokinase-type plasminogen activator and streptokinase and increased binding to a fibrin clot. Fibrin clot lysis mediated by tissue-type plasminogen activator was accelerated for the variants as a result of a lower Km for tissue-type plasminogen activator-mediated plasminogen activation, resulting from the increased affinity of rPlg (variants) for intact fibrin. We conclude that the basic residues in the extremely plasmin susceptible hinge region of plasminogen are directly involved in maintaining the activation resistant Glu1-plasminogen conformation.
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PMID:The activation-resistant conformation of recombinant human plasminogen is stabilized by basic residues in the amino-terminal hinge region. 779 79

Here we report the crystal structure at approximately 4-A resolution of a selectively proteolyzed bovine fibrinogen. This key component in hemostasis is an elongated 340-kDa glycoprotein in the plasma that upon activation by thrombin self-assembles to form the fibrin clot. The crystals are unusual because they are made up of end-to-end bonded molecules that form flexible filaments. We have visualized the entire coiled-coil region of the molecule, which has a planar sigmoidal shape. The primary polymerization receptor pockets at the ends of the molecule face the same way throughout the end-to-end bonded filaments, and based on this conformation, we have developed an improved model of the two-stranded protofibril that is the basic building block in fibrin. Near the middle of the coiled-coil region, the plasmin-sensitive segment is a hinge about which the molecule adopts different conformations. This segment also includes the boundary between the three- and four-stranded portions of the coiled coil, indicating the location on the backbone that anchors the extended flexible Aalpha arm. We suggest that a flexible branch point in the molecule may help accommodate variability in the structure of the fibrin clot.
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PMID:The crystal structure of modified bovine fibrinogen. 1061 75

Phosphoglycerate kinase (PGK) is secreted by tumor cells and facilitates reduction of disulfide bond(s) in plasmin (Lay, A. J., Jiang, X.-M., Kisker, O., Flynn, E., Underwood, A., Condron, R., and Hogg, P. J. (2000) Nature 408, 869-873). The angiogenesis inhibitor, angiostatin, is cleaved from the reduced plasmin by a combination of serine- and metalloproteinases. The chemistry of protein reductants is typically mediated by a pair of closely spaced Cys residues. There are seven Cys in human PGK, and mutation of all seven to Ala did not appreciably affect plasmin reductase activity, although some of the mutations perturbed the tertiary structure of the protein. Cys-379 and Cys-380 are close to the hinge that links the N- and C-terminal domains of PGK. Alkylation/oxidation of Cys-379 and -380 by four different thiol-reactive compounds reduced plasmin reductase activity to 7--35% of control. Binding of 3-phosphoglycerate and/or MgATP to the N- and C-terminal domains of PGK, respectively, triggers a hinge bending conformational change in the enzyme. Incubation of PGK with 3-phosphoglycerate and/or MgATP ablated plasmin reductase activity, with half-maximal inhibitory effects at approximately 1 mm concentration. In summary, reduction of plasmin by PGK is a thiol-independent process, although either alkylation/oxidation of the fast-reacting Cys near the hinge or hinge bending conformational change in PGK perturbs plasmin reduction by PGK, perhaps by obstructing the interaction of plasmin with PGK or perturbing conformational changes in PGK required for plasmin reduction.
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PMID:Plasmin reduction by phosphoglycerate kinase is a thiol-independent process. 1178 84

Fibrinogen is a serum multi-chain protein which, when activated, aggregates to form fibrin, one of the main components of a blood clot. Fibrinolysis controls blood clot dissolution through the action of the enzyme plasmin, which cleaves fibrin at specific locations. Although the main biochemical factors involved in fibrin formation and lysis have been identified, a clear mechanistic picture of how these processes take place is not available yet. This picture would be instrumental, for example, for the design of improved thrombolytic or anti-haemorrhagic strategies, as well as, materials with improved biocompatibility. Here, we present extensive molecular dynamics simulations of fibrinogen which reveal large bending motions centered at a hinge point in the coiled-coil regions of the molecule. This feature, likely conserved across vertebrates according to our analysis, suggests an explanation for the mechanism of exposure to lysis of the plasmin cleavage sites on fibrinogen coiled-coil region. It also explains the conformational variability of fibrinogen observed during its adsorption on inorganic surfaces and it is supposed to play a major role in the determination of the hydrodynamic properties of fibrinogen. In addition the simulations suggest how the dynamics of the D region of fibrinogen may contribute to the allosteric regulation of the blood coagulation cascade through a dynamic coupling between the a- and b-holes, important for fibrin polymerization, and the integrin binding site P1.
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PMID:The Internal Dynamics of Fibrinogen and Its Implications for Coagulation and Adsorption. 2636 80