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Regulating Hemostasis: The Factor Va Cofactor Effect

Joesph, Wiencek R.
http://rave.ohiolink.edu/etdc/view?acc_num=csu1431514489

Abstract Details

2015, Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, College of Sciences and Health Professions.
Single chain factor V (fV) circulates in blood as a quiescent procofactor. Timely removal of the B-domain and generation of factor Va (fVa) is required for expression of fVa cofactor activity which is manifested by binding to factor Xa (fXa) on a membrane surface at the place of a vascular injury in the presence of Ca2+ ions to form prothrombinase. Incorporation of fVa into the prothrombinase complex, results in a 300,000-fold overall increase in the catalytic efficiency of the enzyme compared to fXa-alone. Cleavage at Arg271 and Arg320 of prothrombin is required to form the active serine protease α-thrombin. Our findings demonstrate that amino acid region 1000-1008 of the B-domain of fV keeps the procofactor in a quiescent state. Furthermore, we provide unequivocal evidence for the existence of a third distinct exosite within prothrombin providing: 1) the fVa-dependent recognition site for fXa in prothrombinase required for efficient prothrombin activation, and 2) a novel exosite compulsory for appropriate tethering of fV and fVIII required for their timely activation by α-thrombin. Overall, our work offers original information for the intimate role of fVa during the clotting process in directing prothrombin cleavage by fXa as follows: following vascular injury the newly formed membrane-bound fXa attempts to slowly activate prothrombin through three sequential cleavages: initial cleavage at Arg155 is followed by cleavage at Arg271 with cleavage at Arg320 occurring last. Minute amounts of fVa formed in this fXa-rich environment will form prothrombinase and inhibit membrane-bound fXa cleavage of prothrombin at Arg155, while promoting initial cleavage of prothrombin by the enzyme at Arg271. As more fVa is produced and following saturation of fXa with fVa the cofactor redirects initial cleavage of prothrombin by fXa at Arg320 by promoting its binding to the fVa-dependent site on prothrombin close to (pro)exosite I.
Michael Kalafatis, PhD (Committee Chair)
Edward Plow, PhD (Committee Member)
Kathleen Berkner, PhD (Committee Member)
David Anderson, PhD (Committee Member)
Anton Komar, PhD (Committee Member)
199 p.
Biochemistry; Chemistry; Molecular Biology
Factor Va, Prothrombin, Prothrombinase, Coagulation

Recommended Citations

Citations

  • Joesph, W. R. (2015). Regulating Hemostasis: The Factor Va Cofactor Effect [Doctoral dissertation, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1431514489

    APA Style (7th edition)

  • Joesph, Wiencek. Regulating Hemostasis: The Factor Va Cofactor Effect. 2015. Cleveland State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1431514489.

    MLA Style (8th edition)

  • Joesph, Wiencek. "Regulating Hemostasis: The Factor Va Cofactor Effect." Doctoral dissertation, Cleveland State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1431514489

    Chicago Manual of Style (17th edition)

csu1431514489
473
© 2015, all rights reserved.
This open access ETD is published by Cleveland State University and OhioLINK.