Triabin, a Highly Potent Exosite Inhibitor of Thrombin
1995/12/01 by Christiane Noeske‐Jungblut, Christiane Noeske-Jungblut, Bernard Haendler +7 · 27 citations
Biochemistry, Genetics and Molecular Biology · Chemistry · #Benzamidine #Biochemical and Structural Characterization #Biochemistry #Biology #Chemistry #Discovery and development of direct thrombin inhibitors #Enzyme #Immunology #Molecular biology #Partial thromboplastin time #Platelet #Signaling Pathways in Disease #Thrombin #Thrombin time #Thrombomodulin #Venomous Animal Envenomation and Studies
paper · pdf · doi:10.1074/jbc.270.48.28629
openalex publication_date 1995/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
Abstract
Triabin, a new thrombin inhibitor, has been purified from the saliva of Triatoma pallidipennis, a blood-sucking triatomine bug. It forms a noncovalent complex with thrombin at a molar ratio of 1:1, inhibits thrombin-induced platelet aggregation, and prolongs thrombin clotting time and activated partial thromboplastin time. However, it only minimally suppresses the amidolytic activity of thrombin, as measured by a chromogenic peptide substrate assay. It completely blocks trypsin-catalyzed cleavage of thrombin, probably via protection of the anion-binding exosite and inhibits the effect of thrombomodulin on thrombin in a dose-dependent fashion. These results indicate that the inhibitor is directed toward the anion-binding exosite of thrombin. The protein was partially sequenced and the information used to isolate cDNA clones from a T. pallidipennis salivary gland library. Four slightly polymorphic variants coding for mature proteins of 142 amino acids preceded by a putative leader sequence were obtained. The recombinant protein expressed in the periplasmic space of Escherichia coli has a biological activity similar to that of salivary triabin, as tested in a thrombin-induced platelet aggregation assay. In addition, recombinant triabin inhibits thrombin-catalyzed hydrolysis of fibrinogen with a Ki of about 3 pM.
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