Identification and Characterization of the Thrombin Binding Sites on Fibrin

Authors

David A. Meh, University of Wisconsin Medical SchoolFollow
Kevin R. Siebenlist, Marquette UniversityFollow
Michael W. Mosesson, University of Wisconsin Medical SchoolFollow

Document Type

Article

Publication Date

9-1996

Publisher

American Society for Biochemistry and Molecular Biology

Source Publication

Journal of Biological Chemistry

Source ISSN

0021-9258

Original Item ID

DOI: 10.1074/jbc.271.38.23121

Abstract

Thrombin binds to fibrin at two classes of non-substrate sites, one of high affinity and the other of low affinity. We investigated the location of these thrombin binding sites by assessing the binding of thrombin to fibrin lacking or containing γ′ chains, which are fibrinogen γ chain variants that contain a highly anionic carboxyl-terminal sequence. We found the high affinity thrombin binding site to be located exclusively in D domains on γ′ chains (K_a, 4.9 × 10⁶⁻¹; n, 1.05 per γ′ chain), whereas the low affinity thrombin binding site was in the fibrin E domain (K_a, 0.29 × 10⁶⁻¹; n, 1.69 per molecule). The amino-terminal β15-42 fibrin sequence is an important constituent of low affinity binding, since thrombin binding at this site is greatly diminished in fibrin molecules lacking this sequence. The tyrosine-sulfated, thrombin exosite-binding hirudin peptide, S-Hir^53-64 (hirugen), inhibited both low and high affinity thrombin binding to fibrin (IC50 1.4 and 3.0 μ, respectively). The presence of the high affinity γ′ chain site on fibrinogen molecules did not inhibit fibrinogen conversion to fibrin as assessed by thrombin time measurements, and thrombin exosite binding to fibrin at either site did not inhibit its catalytic activity toward a small thrombin substrate, S-2238. We infer from these findings that there are two low affinity non-substrate thrombin binding sites, one in each half of the dimeric fibrin E domain, and that they may represent a residual aspect of thrombin binding and cleavage of its substrate fibrinogen. The high affinity thrombin binding site on γ′ chains is a constitutive feature of fibrin as well as fibrinogen.

Comments

Published version. Journal of Biological Chemistry, Vol. 271, No. 38 (September 1996): 23151-23125. DOI. © 1996 American Society for Biochemistry and Molecular Biology. Used with permission.

Recommended Citation

Meh, David A.; Siebenlist, Kevin R.; and Mosesson, Michael W., "Identification and Characterization of the Thrombin Binding Sites on Fibrin" (1996). Biomedical Sciences Faculty Research and Publications. 244.
https://epublications.marquette.edu/biomedsci_fac/244