Evidence that Catalytically-Inactivated Thrombin Forms Dimers That Bridge between Fibrin/Fibrinogen Fibers and Enhance Polymerization

Authors

Michael W. Mosesson, Blood Center of WisconsinFollow
Irene Hernandez, Washington University School of Medicine in St. LouisFollow
Kevin R. Siebenlist, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

7-1-2004

Publisher

Elsevier

Source Publication

Biophysical Chemistry

Source ISSN

0301-4622

Original Item ID

doi: 10.1016/j.bpc.2004.01.007

Abstract

Phe-pro-arg-chloromethyl ketone-inhibited α-thrombin [FPRα-thr] retains its fibrinogen recognition site (exosite 1), augments fibrin/fibrinogen [fibrin(ogen)] polymerization, and increases the incorporation of fibrin into clots. There are two ‘low-affinity’ thrombin-binding sites in each central E domain of fibrin, plus a non-substrate ‘high affinity’ γ′ chain thrombin-binding site on heterodimeric ‘fibrin(ogen) 2’ molecules (γ_A,γ′). ‘Fibrin(ogen) 1’ (γ_A, γ_A) containing only low-affinity thrombin-binding sites, showed concentration-dependent FPRα-thr enhancement of polymerization, thus indicating that low-affinity sites are sufficient for enhancing polymerization. FPRγ-thr, whose exosite 1 is non-functional, did not enhance polymerization of either fibrin(ogen)s 1 or 2 and DNA aptamer HD-1, which binds specifically to exosite 1, blocked FPRα-thr enhanced polymerization of both types of fibrin(ogen) (1>2). These results showed that exosite 1 is the critical element in thrombin that mediates enhanced fibrin polymerization. Des Bβ1-42 fibrin(ogen) 1, containing defective ‘low-affinity’ binding sites, was subdued in its FPRα-thr-mediated reactivity, whereas des Bβ1-42 fibrin(ogen) 2 (γ_A,γ′) was more reactive. Thus, the γ′ chain thrombin-binding site contributes to enhanced FPRα-thr mediated polymerization and acts through a site on thrombin that is different from exosite 1, possibly exosite 2. Overall, the results suggest that during fibrin clot formation, catalytically-inactivated FPRα-thr molecules form non-covalently linked thrombin dimers, which serve to enhance fibrin polymerization by bridging between fibrin(ogen) molecules, mainly through their low affinity sites.

Comments

Biophysical Chemistry, Vol. 110, No. 1-2 (July 1, 2004): 93-100. DOI.

Recommended Citation

Mosesson, Michael W.; Hernandez, Irene; and Siebenlist, Kevin R., "Evidence that Catalytically-Inactivated Thrombin Forms Dimers That Bridge between Fibrin/Fibrinogen Fibers and Enhance Polymerization" (2004). Biomedical Sciences Faculty Research and Publications. 42.
https://epublications.marquette.edu/biomedsci_fac/42