scholarly journals NMR structure determination of Ixolaris and factor X(a) interaction reveals a noncanonical mechanism of Kunitz inhibition

Blood ◽  
2019 ◽  
Vol 134 (8) ◽  
pp. 699-708 ◽  
Author(s):  
Viviane S. De Paula ◽  
Nikolaos G. Sgourakis ◽  
Ivo M. B. Francischetti ◽  
Fabio C. L. Almeida ◽  
Robson Q. Monteiro ◽  
...  
Keyword(s):  
Factor Xa ◽  
Coagulation Factor ◽  
Structural Basis ◽  
Factor X ◽  
Heparin Binding ◽  
Nmr Structure Determination ◽  
High Resolution Structure ◽  
Function Relationship ◽  
Affinity Interaction ◽  
Relationship Of

Abstract Ixolaris is a potent tick salivary anticoagulant that binds coagulation factor Xa (FXa) and zymogen FX, with formation of a quaternary tissue factor (TF)/FVIIa/ FX(a)/Ixolaris inhibitory complex. Ixolaris blocks TF-induced coagulation and PAR2 signaling and prevents thrombosis, tumor growth, and immune activation. We present a high-resolution structure and dynamics of Ixolaris and describe the structural basis for recognition of FX. Ixolaris consists of 2 Kunitz domains (K1 and K2) in which K2 is strikingly dynamic and encompasses several residues involved in FX binding. This indicates that the backbone plasticity of K2 is critical for Ixolaris biological activity. Notably, a nuclear magnetic resonance–derived model reveals a mechanism for an electrostatically guided, high-affinity interaction between Ixolaris and FX heparin-binding (pro)exosite, resulting in an allosteric switch in the catalytic site. This is the first report revealing the structure-function relationship of an anticoagulant targeting a zymogen serving as a scaffold for TF inhibition.

Activation of Human Coagulation Factor VIII by Activated Factor X, the Common Product of the Intrinsic and the Extrinsic Pathway of Blood Coagulation

1982 ◽  
Vol 47 (02) ◽  
pp. 096-100 ◽  
Author(s):  
K Mertens ◽  
R M Bertina
Keyword(s):  
Factor Viii ◽  
Human Factor ◽  
Intrinsic Factor ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Factor X ◽  
Extrinsic Factor ◽  
Extrinsic Pathway ◽  
Factor Ixa ◽  
The Common

SummaryThe intrinsic activation of human factor X has been studied in a system consisting of purified factors and in plasma. In both these systems factor Xa stimulated the activation of factor X by factor IXa plus factor VIII This is due to the activation of factor VIII by factor Xa. When this factor Xa is formed via the extrinsic pathway, the extrinsic factor X activator functions as a stimulator of the intrinsic factor X activator.

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.

Antithrombin ‘DREUX’ (Lys114Glu): A Variant with Complete Loss of Heparin Affinity

2002 ◽  
Vol 88 (09) ◽  
pp. 436-443 ◽  
Author(s):  
James Huntington ◽  
Jacqueline Conard ◽  
Robin Carrell ◽  
Alec Mushunje ◽  
Aiwu Zhou
Keyword(s):  
Factor Xa ◽  
Fold Increase ◽  
Complete Loss ◽  
Factor X ◽  
Heparin Binding ◽  
High Affinity ◽  
The Core ◽  
Factor Xa Inhibition ◽  
Heparin Affinity ◽  
Father And Son

SummaryHere we report the finding of a new natural antithrombin mutation that confirms the critical contribution of lysine 114 to the binding of the core heparin pentasaccharide, with the replacement of lysine 114 by glutamate causing a complete loss in affinity. The variant was identified in a father and son, the father having been investigated for an episode of cerebral ischaemia associated with hypercholesterolaemia. The variant forms SDS-stable complexes with activated factor X (fXa) and its thermal stability and rate of factor Xa inhibition in the absence of heparin are identical to those of normal antithrombin. Normal antithrombin binds to the high affinity heparin pentasaccharide with a Kd of 1nM, as detected by a 45% change in intrinsic fluorescence, resulting in a 230-fold increase in rate of factor Xa inhibition. However, no change in fluorescence was detected for the variant when titrated with heparin or the heparin pentasaccharide, nor was there detectable activation towards factor Xa, indicating a complete loss of heparin binding.

scholarly journals The Low-Density Lipoprotein Receptor-Related Protein (LRP) Mediates Clearance of Coagulation Factor Xa In Vivo

Blood ◽  
1998 ◽  
Vol 91 (2) ◽  
pp. 555-560 ◽  
Author(s):  
Masaaki Narita ◽  
Amy E. Rudolph ◽  
Joseph P. Miletich ◽  
Alan L. Schwartz
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Lipoprotein Receptor ◽  
Factor X ◽  
Receptor Associated Protein ◽  
Density Lipoprotein Receptor ◽  
Lipoprotein Receptor Related Protein

Abstract Blood coagulation factor X plays a pivotal role in the clotting cascade. When administered intravenously to mice, the majority of activated factor X (factor Xa) binds to α2-macroglobulin (α2M) and is rapidly cleared from the circulation into liver. We show here that the low-density lipoprotein receptor-related protein (LRP) is responsible for factor Xa catabolism in vivo. Mice overexpressing a 39-kD receptor-associated protein that binds to LRP and inhibits its ligand binding activity displayed dramatically prolonged plasma clearance of 125I-factor Xa. Preadministration of α2M-proteinase complexes (α2M*) also diminished the plasma clearance of125I-factor Xa in a dose-dependent fashion. The clearance of preformed complexes of 125I-factor Xa and α2M was similar to that of 125I-factor Xa alone and was also inhibited by mice overexpressing a 39-kD receptor-associated protein. These results thus suggest that, in vivo, factor Xa is metabolized via LRP after complex formation with α2M.

scholarly journals Pathways in the activation of human coagulation factor X

1980 ◽  
Vol 185 (3) ◽  
pp. 647-658 ◽  
Author(s):  
K Mertens ◽  
R M Bertina
Keyword(s):  
Heavy Chain ◽  
Active Form ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Terminal Region ◽  
Factor Vii ◽  
Factor X ◽  
Catalytically Active ◽  
A Site ◽  
Polypeptide Chains

Purified human Factor X (apparent mol.wt. 72000), which consists of two polypeptide chains (mol.wt. 55000 and 19000), was activated by both Russell's-viper venom and the purified physiological activators (Factor VII/tissue factor and Factor IXa/Factor VIII). They all convert Factor X to catalytically active Factor Xa (mol.wt. 54000) by cleaving the heavy chain at a site on the N-terminal region. In the presence of Ca2+ and phospholipid, the Factor Xa formed catalyses (a) the cleavage of a small peptide (mol.wt. 4000) from the C-terminal region of the heavy chain of Factor Xa, resulting in a second active form (mol.wt. 50000), and (b) the cleavage of a peptide containing the active-site serine residue (mol.wt. 13000) from the C-terminal region of the heavy chain of Factor X, resulting in an inactivatable component (mol.wt. 59000). A nomenclature for the various products is proposed.

Releasing the brakes in coagulation Factor IXa by co-operative maturation of the substrate-binding site

2016 ◽  
Vol 473 (15) ◽  
pp. 2395-2411 ◽  
Author(s):  
Line Hyltoft Kristensen ◽  
Ole H. Olsen ◽  
Grant E. Blouse ◽  
Hans Brandstetter
Keyword(s):  
Coagulation Factor ◽  
Factor Ix ◽  
Fine Tuning ◽  
Structural Basis ◽  
Factor X ◽  
Multifaceted Approach ◽  
Factor Ixa ◽  
Activated Platelets ◽  
Factor Viiia ◽  
Multiple Regions

Coagulation Factor IX is positioned at the merging point of the intrinsic and extrinsic blood coagulation cascades. Factor IXa (activated Factor IX) serves as the trigger for amplification of coagulation through formation of the so-called Xase complex, which is a ternary complex of Factor IXa, its substrate Factor X and the cofactor Factor VIIIa on the surface of activated platelets. Within the Xase complex the substrate turnover by Factor IXa is enhanced 200000-fold; however, the mechanistic and structural basis for this dramatic enhancement remains only partly understood. A multifaceted approach using enzymatic, biophysical and crystallographic methods to evaluate a key set of activity-enhanced Factor IXa variants has demonstrated a delicately balanced bidirectional network. Essential molecular interactions across multiple regions of the Factor IXa molecule co-operate in the maturation of the active site. This maturation is specifically facilitated by long-range communication through the Ile212–Ile213 motif unique to Factor IXa and a flexibility of the 170-loop that is further dependent on the conformation in the Cys168–Cys182 disulfide bond. Ultimately, the network consists of compensatory brakes (Val16 and Ile213) and accelerators (Tyr99 and Phe174) that together allow for a subtle fine-tuning of enzymatic activity.

scholarly journals Regions 301–303 and 333–339 in the catalytic domain of blood coagulation Factor IX are Factor VIII-interactive sites involved in stimulation of enzyme activity

1999 ◽  
Vol 339 (2) ◽  
pp. 217-221 ◽  
Author(s):  
Joost A. KOLKMAN ◽  
Peter J. LENTING ◽  
Koen MERTENS
Keyword(s):  
Catalytic Domain ◽  
Coagulation Factor ◽  
Factor Ix ◽  
Factor X ◽  
Factor Ixa ◽  
Factor Viiia ◽  
Α Helix ◽  
Factor X Activation ◽  
Affinity Interaction ◽  
Stimulation Of

The contribution of the Factor IX catalytic domain to Factor VIIIa binding has been evaluated by functional analysis of Factor IX variants with substitutions in α-helix region 333–339 and region 301–303. These regions were found to play a prominent role in Factor VIIIa-dependent stimulation of Factor X activation, but do not contribute to the high-affinity interaction with Factor VIIIa light chain. We propose that complex assembly between Factor IXa and Factor VIIIa involves multiple interactive sites that are located on different domains of these proteins.

Sign in / Sign up

Export Citation Format

Share Document