scholarly journals Mechanism by Which Exosites Promote the Inhibition of Blood Coagulation Proteases by Heparin-activated Antithrombin

2007 ◽  
Vol 282 (46) ◽  
pp. 33609-33622 ◽  
Author(s):  
Gonzalo Izaguirre ◽  
Richard Swanson ◽  
Srikumar M. Raja ◽  
Alireza R. Rezaie ◽  
Steven T. Olson
Keyword(s):  
Blood Coagulation ◽  
Conformational Change ◽  
Blood Clotting ◽  
Factor Xa ◽  
Kinetic Studies ◽  
Complex Interaction ◽  
Wild Type ◽  
Site Specific ◽  
Equilibrium Binding ◽  
Diffusion Controlled

Heparin activates the serpin, antithrombin, to inhibit its target blood-clotting proteases by generating new protease interaction exosites. To resolve the effects of these exosites on the initial Michaelis docking step and the subsequent acylation and conformational change steps of antithrombin-protease reactions, we compared the reactions of catalytically inactive S195A and active proteases with site-specific fluorophore-labeled antithrombins that allow monitoring of these reaction steps. Heparin bound to N,N′-dimethyl-N-(acetyl)-N′-(7-nitrobenz-3-oxa-1,3-diazol-4-yl)ethylenediamine (NBD)-fluorophore-labeled antithrombins and accelerated the reactions of the labeled inhibitor with thrombin and factor Xa similar to wild type. Equilibrium binding of NBD-labeled antithrombins to S195A proteases showed that exosites generated by conformationally activating antithrombin with a heparin pentasaccharide enhanced the affinity of the serpin for S195A factor Xa minimally 100-fold. Moreover, additional bridging exosites provided by a hexadecasaccharide heparin activator enhanced antithrombin affinity for both S195A factor Xa and thrombin at least 1000-fold. Rapid kinetic studies showed that these exosite-mediated enhancements in Michaelis complex affinity resulted from increases in kon and decreases in koff and caused antithrombin-protease reactions to become diffusion-controlled. Competitive binding and kinetic studies with exosite mutant antithrombins showed that Tyr-253 was a critical mediator of exosite interactions with S195A factor Xa; that Glu-255, Glu-237, and Arg-399 made more modest contributions to these interactions; and that exosite interactions reduced koff for the Michaelis complex interaction. Together these results show that exosites generated by heparin activation of antithrombin function both to promote the formation of an initial antithrombin-protease Michaelis complex and to favor the subsequent acylation of this complex.

Two parallel prothrombin activator systems in Australian rough-scaled snake, Tropidechis carinatus

2005 ◽  
Vol 93 (01) ◽  
pp. 40-47 ◽  
Author(s):  
Md. Abu Reza ◽  
Sanjay Swarup ◽  
Manjunatha Kini
Keyword(s):  
Blood Coagulation ◽  
Blood Clotting ◽  
Cdna Sequence ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Venom Gland ◽  
Factor X ◽  
Specific Expression ◽  
Life Saving ◽  
Sequence Encoding

SummaryIt is uncommon for similar pathways/systems to be involved in highly divergent functions within single organisms. Earlier, we have shown that trocarin D, a venom prothrombin activator, from the Australian rough-scaled snake Tropidechis carinatus, is structurally and functionally similar to the blood coagulation factor Xa (FXa). The presence of a haemostatic system in these snakes implies that they have two parallel prothrombin activating systems: one in the plasma, that participates in the life saving process of blood clotting and the other in their venom, where it acts as a toxin. Here, we report the complete cDNA sequence encoding the blood coagulation factor X (FX) from the liver of T. carinatus. Deduced T. carinatus FX sequence shows ~80% identity with trocarin D but ~50% identity with the mammalian FX. Our present study confirms the presence of two separate genes – one each for FX and trocarin D, that code for similar proteins in T. carinatus snake. These two genes have different expression sites and divergent uses suggesting that snake venom prothrombin activators have probably evolved by the duplication of the liver FX gene and subsequently marked for tissue-specific expression in the venom gland.

scholarly journals Highly Procoagulant Extracellular Vesicles in Amniotic Fluid

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 4961-4961
Author(s):  
Johannes Thaler ◽  
Lena Hell ◽  
Lukas Wisgrill ◽  
Andreas Spittler ◽  
Michael Schwameis ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Amniotic Fluid ◽  
Blood Coagulation ◽  
Extracellular Vesicles ◽  
Whole Blood ◽  
Blood Clotting ◽  
Factor Xa ◽  
Coagulation Cascade ◽  
Contact Activation ◽  
Plasma Factor

Abstract Background: The pathomechanisms underlying disseminated intravascular coagulation (DIC) following amniotic fluid (AF) embolism remain to be fully elucidated. Highly procoagulant phosphatidylserine (PS)- and tissue factor (TF) expressing extracellular vesicles (EVs) might play a central role. Objective: To perform extensive analyses of the procoagulant properties of AF with a panel of functional coagulation assays and flow cytometry to investigate the pathogenesis of AF induced DIC. Methods: A prothrombinase assay, an EV-TF dependent factor Xa (FXa) generation assay, a modified thrombin- and fibrin-generation assay, a whole blood clotting model and flow cytometry were applied in AF- and control plasma. Results: Phosphatidylserine expression was 21-fold increased in AF compared to plasma. Factor Xa generation was extremely high when TF-expressing EVs from AF were co-incubated with recombinant FVIIa. In the thrombin- and fibrin generation assay AF-derived EVs strongly activated the blood coagulation cascade via PS and TF. In a whole blood clotting model AF-derived TF-expressing EVs significantly shortened the clotting time from 734 ± 139 seconds in the presence- to 232 ± 139 seconds in the absence of an anti-TF antibody. The contact activation pathway via factor FXII was not affected. Applying flow cytometry, a sub-population of PS- and TF co-expressing EVs was clearly identified in AF. Conclusions: We thoroughly investigated the effect of AF on blood coagulation and found that PS+ and TF+ EVs determine its procoagulant potential. Taken together our data further delineate the pathomechanisms underlying AF-induced coagulopathy, which could improve diagnostic- and treatment modalities. Disclosures No relevant conflicts of interest to declare.

Cellular Consequences of the Initiation of Blood Coagulation

1999 ◽  
Vol 82 (08) ◽  
pp. 183-192 ◽  
Author(s):  
Eric Camerer ◽  
John-Arne Røttingen ◽  
Merete Thune Wiiger ◽  
Elisabet Gjernes ◽  
Hans Prydz
Keyword(s):  
Endothelial Cells ◽  
Blood Coagulation ◽  
Intracellular Signaling ◽  
Blood Clotting ◽  
Factor Viia ◽  
Three Dimensional ◽  
Factor Xa ◽  
Factor Vii ◽  
Dimensional Structure ◽  
Major Player

IntroductionThis paper reviews some of the cell biological aspects of the consequences of blood clotting initiation. These intracellular events occur in cells carrying tissue factor (TF) when its ligand, factor VIIa, is bound to the receptor-like TF surface molecules. The intracellular signaling generated by this ligand/receptor binding and some of its consequences are described and parallel experiments with factor Xa are discussed.The role of TF as a major player in the initiation of blood coagulation has been known since the last century1,2 and is now characterized in molecular detail. Research on TF, for a long period and for obvious reasons, concentrated on its essential role as a cofactor in this process. Its importance in the development of clinical thrombosis, be it venous or arterial, has been appreciated since it was discovered that monocytes and macrophages3 and endothelial cells,4 under certain conditions, could be induced to synthesize TF. This contributed to answering the previously unresolved question about how TF got into contact with the flowing blood in the absence of any trauma. We later demonstrated that the TF induction process, in many cases, is subject to down-regulation by cAMP5,6 and that Ca2+ influx can induce the synthesis,5,6 along with a large number of other compounds.7 We also showed that protein kinase C was a mediator in at least some of these inducing pathways.8 The purification of TF in 19739 showed that TF was an integral membrane protein. By 1977 it was clear that TF likely participated in functions other than blood clotting.10 The cloning of the gene for TF11-14 suggested that, structurally, TF was a member of the Class II cytokine receptor family.15 To fulfil the criteria for being a true receptor, it also needed a specific and high-affinity ligand, which it has in factor VII. Also, to be classified as a true receptor, ligand binding should generate an intracellular signal. In 1992, we presented the first report of such a signal in the form of Ca2+ peaks. These peaks were triggered by the addition of factor VIIa to endothelial cells carrying TF on their surface as a result of exposure to interleukin 1β. These signals were characterized further16,17 and were thought to render final proof for the function of the TF receptor.This review discusses our findings with respect to TF/factor VIIa-induced intracellular Ca2+-signaling and concludes that there is likely a two-component receptor. The more consequential question—whether this intracellular signaling leads to altered gene expression and to other phenotypic changes—is also raised. The establishment of knockout mice18–20 and efforts to solve the three-dimensional structure of this complex by x-ray diffraction21–24 are not reviewed extensively.

Blood Coagulation Studies and Extracorporeal Circulation in Man

1967 ◽  
Vol 18 (03/04) ◽  
pp. 634-646 ◽  
Author(s):  
N Thurnherr
Keyword(s):  
Blood Coagulation ◽  
Extracorporeal Circulation ◽  
Blood Clotting ◽  
Heart Surgery ◽  
Open Heart Surgery ◽  
Fibrinolytic System ◽  
Open Heart ◽  
Clotting Factors ◽  
Blood Clotting Factors

SummaryBlood clotting investigations have been executed in 25 patients who have undergone open heart surgery with extracorporeal circulation. A description of alterations in the activity of blood clotting factors, the fibrinolytic system, prothrombin consumption and platelets during several phases of the operation is given.

Human Prothrombin Activation: Determination of Plasma and Serum Levels of Prothrombin Fragment 3 by Radioimmunoassay

1979 ◽  
Author(s):  
Daniel Walz ◽  
Thomas Brown
Keyword(s):  
Blood Clotting ◽  
Factor Xa ◽  
Heart Association ◽  
Serum Levels ◽  
Cross Reactivity ◽  
Assay Procedure ◽  
A Chain ◽  
Prothrombin Activation ◽  
Theoretical Amount

Human prothrombin activation is unique in that, in addition to the release of fragment 1.2 (FI.2) from the NH-terminus of prothrombin by factor Xa during the generation of thrombin, an additional 13 residue polypeptide, fragment 3 (F3), is autocatalytically removed from the amino-terminus of the thrombin A chain. We have developed a rapid radioimmunoassay for human F3 which incorporates short incubation times and the use of a preprecipitated second antibody; the assay can be performed in three hours. Specificity studies in buffer systems show prothrombin and prethrombin 1 cross-reacting at a level of 0.001; purified thrombin does not cross-react. In the presence of 5% BSA, prothrombin displays considerably less cross-reactivity. No immunoreactive material to F3 antibodies could be detected in 400 μL of plasma. Serum, obtained from whole blood clotting, contained measurable quantities of F3 (40-100 ng/mL). This amount in serum represents only 5-10% of the theoretical amount available should all of the fragment be hydrolytically cleaved during the conversion of prothrombin to thrombin. This assay procedure is currently being utilized to monitor the activation of purified human prothrombin in the absence and presence of selected plasma inhibitors. (Supported in part by NIH 05384-17 and the Michigan Heart Association).

scholarly journals Functional expression of a yeast mitochondrial intron-encoded protein requires RNA processing at a conserved dodecamer sequence at the 3' end of the gene.

1989 ◽  
Vol 9 (4) ◽  
pp. 1507-1512 ◽  
Author(s):  
H Zhu ◽  
H Conrad-Webb ◽  
X S Liao ◽  
P S Perlman ◽  
R A Butow
Keyword(s):  
Genetic Analysis ◽  
Rna Processing ◽  
Fold Increase ◽  
Functional Expression ◽  
Rrna Gene ◽  
Yeast Mitochondria ◽  
Wild Type ◽  
Site Specific ◽  
Var1 Gene ◽  
A Site

All mRNAs of yeast mitochondria are processed at their 3' ends within a conserved dodecamer sequence, 5'-AAUAAUAUUCUU-3'. A dominant nuclear suppressor, SUV3-I, was previously isolated because it suppresses a dodecamer deletion at the 3' end of the var1 gene. We have tested the effects of SUV3-1 on a mutant containing two adjacent transversions within a dodecamer at the 3' end of fit1, a gene located within the 1,143-base-pair intron of the 21S rRNA gene, whose product is a site-specific endonuclease required in crosses for the quantitative transmission of that intron to 21S alleles that lack it. The fit1 dodecamer mutations blocked both intron transmission and dodecamer cleavage, neither of which was suppressed by SUV3-1 when present in heterozygous or homozygous configurations. Unexpectedly, we found that SUV3-1 completely blocked cleavage of the wild-type fit1 dodecamer and, in SUV3-1 homozygous crosses, intron conversion. In addition, SUV3-1 resulted in at least a 40-fold increase in the amount of excised intron accumulated. Genetic analysis showed that these phenotypes resulted from the same mutation. We conclude that cleavage of a wild-type dodecamer sequence at the 3' end of the fit1 gene is essential for fit1 expression.

Effects of viscosity and osmotic stress on the reaction of human butyrylcholinesterase with cresyl saligenin phosphate, a toxicant related to aerotoxic syndrome: kinetic and molecular dynamics studies

2013 ◽  
Vol 454 (3) ◽  
pp. 387-399 ◽  
Author(s):  
Patrick Masson ◽  
Sofya Lushchekina ◽  
Lawrence M. Schopfer ◽  
Oksana Lockridge
Keyword(s):  
Osmotic Stress ◽  
Osmotic Pressure ◽  
Active Site ◽  
Md Simulations ◽  
Catalytic Triad ◽  
Wild Type ◽  
Irreversible Inhibitor ◽  
Enzyme Active Site ◽  
Diffusion Controlled ◽  
Peripheral Site

CSP (cresyl saligenin phosphate) is an irreversible inhibitor of human BChE (butyrylcholinesterase) that has been involved in the aerotoxic syndrome. Inhibition under pseudo-first-order conditions is biphasic, reflecting a slow equilibrium between two enzyme states E and E′. The elementary constants for CSP inhibition of wild-type BChE and D70G mutant were determined by studying the dependence of inhibition kinetics on viscosity and osmotic pressure. Glycerol and sucrose were used as viscosogens. Phosphorylation by CSP is sensitive to viscosity and is thus strongly diffusion-controlled (kon≈108 M−1·min−1). Bimolecular rate constants (ki) are about equal to kon values, making CSP one of the fastest inhibitors of BChE. Sucrose caused osmotic stress because it is excluded from the active-site gorge. This depleted the active-site gorge of water. Osmotic activation volumes, determined from the dependence of ki on osmotic pressure, showed that water in the gorge of the D70G mutant is more easily depleted than that in wild-type BChE. This demonstrates the importance of the peripheral site residue Asp70 in controlling the active-site gorge hydration. MD simulations provided new evidence for differences in the motion of water within the gorge of wild-type and D70G enzymes. The effect of viscosogens/osmolytes provided information on the slow equilibrium E⇌E′, indicating that alteration in hydration of a key catalytic residue shifts the equilibrium towards E′. MD simulations showed that glycerol molecules that substitute for water molecules in the enzyme active-site gorge induce a conformational change in the catalytic triad residue His438, leading to the less reactive form E′.

scholarly journals Site-specific binding of wild-type p53 to cellular DNA is inhibited by SV40 T antigen and mutant p53.

1992 ◽  
Vol 6 (10) ◽  
pp. 1886-1898 ◽  
Author(s):  
J Bargonetti ◽  
I Reynisdottir ◽  
P N Friedman ◽  
C Prives
Keyword(s):  
Specific Binding ◽  
T Antigen ◽  
Mutant P53 ◽  
Wild Type ◽  
Sv40 T Antigen ◽  
Site Specific ◽  
Wild Type P53 ◽  
Cellular Dna
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