Cryo-EM structure of the prothrombin-prothrombinase complex
Eliza A Ruben1, Brock Summers2, Michael J Rau2
1Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO.
Blood
|April 15, 2022
Summary
Structural insights into prothrombinase complex reveal how factor Xa activates prothrombin. Cryo-EM structures elucidate molecular interactions crucial for blood coagulation and hemostasis.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- The coagulation cascade is essential for hemostasis, involving the activation of prothrombin to thrombin by the prothrombinase complex.
- The prothrombinase complex consists of factor Xa (fXa), factor Va (fVa), calcium ions, and phospholipids.
- The precise molecular mechanisms governing prothrombin activation by the prothrombinase complex remain incompletely understood.
Purpose of the Study:
- To elucidate the molecular basis of prothrombin activation by the prothrombinase complex using high-resolution structural methods.
- To provide a detailed structural understanding of the interactions between fVa, fXa, and prothrombin.
Main Methods:
- Cryogenic electron microscopy (cryo-EM) was employed to determine the structures of the fVa-fXa complex.
- Two structures were solved: one free complex and another bound to prothrombin, at resolutions of 5.3-Å and 4.1-Å, respectively.
Main Results:
- The structure of the prothrombin-fVa-fXa complex reveals specific orientations of Gla domains for membrane interaction.
- Curved conformations of prothrombin and fXa bring their protease domains into proximity, stabilized by the A2 domain of fVa.
- Key segments of fVa (ESTVMATRKMHDRLEPEDEE and YDYQNRL) were shown to interact with fXa and prothrombin, respectively, guiding activation pathways.
Conclusions:
- The cryo-EM structure provides a molecular visualization of prothrombin activation, highlighting the meizothrombin pathway.
- The findings suggest a mechanism for cleavage at the alternative R271 site of prothrombin.
- This research advances fundamental knowledge of a critical step in blood coagulation with implications for broader blood interactions.
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