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Allosteric networks in thrombin distinguish procoagulant vs. anticoagulant activities.

ABSTRACT: The serine protease ?-thrombin is a dual-action protein that mediates the blood-clotting cascade. Thrombin alone is a procoagulant, cleaving fibrinogen to make the fibrin clot, but the thrombin-thrombomodulin (TM) complex initiates the anticoagulant pathway by cleaving protein C. A TM fragment consisting of only the fifth and sixth EGF-like domains (TM56) is sufficient to bind thrombin, but the presence of the fourth EGF-like domain (TM456) is critical to induce the anticoagulant activity of thrombin. Crystallography of the thrombin-TM456 complex revealed no significant structural changes in thrombin, suggesting that TM4 may only provide a scaffold for optimal alignment of protein C for its cleavage by thrombin. However, a variety of experimental data have suggested that the presence of TM4 may affect the dynamic properties of the active site loops. In the present work, we have used both conventional and accelerated molecular dynamics simulation to study the structural dynamic properties of thrombin, thrombin:TM56, and thrombin:TM456 across a broad range of time scales. Two distinct yet interrelated allosteric pathways are identified that mediate both the pro- and anticoagulant activities of thrombin. One allosteric pathway, which is present in both thrombin:TM56 and thrombin:TM456, directly links the TM5 domain to the thrombin active site. The other allosteric pathway, which is only present on slow time scales in the presence of the TM4 domain, involves an extended network of correlated motions linking the TM4 and TM5 domains and the active site loops of thrombin.

SUBMITTER: Gasper PM

PROVIDER: S-EPMC3535651 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Allosteric networks in thrombin distinguish procoagulant vs. anticoagulant activities.

Gasper Paul M PM Fuglestad Brian B Komives Elizabeth A EA Markwick Phineus R L PR McCammon J Andrew JA

Proceedings of the National Academy of Sciences of the United States of America 20121128 52

The serine protease α-thrombin is a dual-action protein that mediates the blood-clotting cascade. Thrombin alone is a procoagulant, cleaving fibrinogen to make the fibrin clot, but the thrombin-thrombomodulin (TM) complex initiates the anticoagulant pathway by cleaving protein C. A TM fragment consisting of only the fifth and sixth EGF-like domains (TM56) is sufficient to bind thrombin, but the presence of the fourth EGF-like domain (TM456) is critical to induce the anticoagulant activity of thr ...[more]

PMID: 23197839

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Project description:The two sides of trauma-induced coagulopathy, the hypocoagulable and the hypercoagulable states, are poorly understood. To identify potential mechanisms for venous thromboembolism and bleeding after acute trauma, we estimated changes in circulating procoagulant microparticles (MPs) and thrombin activity during hospitalization for trauma.Whole blood was collected by venipuncture into 3.2% trisodium citrate at 0, 6, 12, 24, and 72 hours after injury and discharge. Platelet-poor plasma was harvested and stored at -80°C until analysis. Thrombin generation was determined using the calibrated automated thrombogram (CAT), reported as lag time (minutes), peak height (nM thrombin), and time to reach peak height (ttPeak, minutes). The concentration of total procoagulant MPs (number/?L) was measured by flow cytometry. Data are presented as median (interquartile range [IQR]).Among 443 trauma patients (1,734 samples; Injury Severity Score [ISS], 13.0 [IQR, 6.0-22.0]; hospital length of stay, 4.0 days [IQR, 2.0-10.0]; age, 48 years [IQR, 28-65]; 70.7% male; 95% with blunt mechanism; mortality, 3.2%), no discernable patterns in thrombin generation or MP concentration were observed over time. The peak height and MPs were significantly different from healthy volunteers and were 337 nM (IQR, 285-395) and 400/?L plasma (IQR, 211-772), respectively. Extreme (defined as highest or lowest 5%) values reflecting a possible "hypercoagulable state" (lag time ? 1.98, peak height ? 486.2, ttPeak ? 3.61, and total procoagulant MP ? 2,278) were reached within 12 hours after acute trauma, while extreme values representing a possible "hypocoagulable state" (lag time ? 18.6, peak height ? 17.8, and ttPeak ? 29.45) were not reached until 1 day to 3 days.Although there was no predictable pattern of coagulopathy observed in each patient after trauma, those who reached extreme values did so relatively early after injury. These findings should be taken into account when designing risk model tools involving coagulation laboratory parameters.Epidemiologic study, level III.

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Allosteric networks in thrombin distinguish procoagulant vs. anticoagulant activities.

Publications

Allosteric networks in thrombin distinguish procoagulant vs. anticoagulant activities.

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