title: Batroxobin binds fibrin with higher affinity and promotes clot expansion to a greater extent than thrombin.
abstract: Batroxobin is a thrombin-like serine protease from the venom of Bothrops atrox moojeni that clots fibrinogen. In contrast to thrombin, which releases fibrinopeptide A and B from the NH2-terminal domains of the Aα- and Bβ-chains of fibrinogen, respectively, batroxobin only releases fibrinopeptide A. Because the mechanism responsible for these differences is unknown, we compared the interactions of batroxobin and thrombin with the predominant γA/γA isoform of fibrin(ogen) and the γA/γ' variant with an extended γ-chain. Thrombin binds to the γ'-chain and forms a higher affinity interaction with γA/γ'-fibrin(ogen) than γA/γA-fibrin(ogen). In contrast, batroxobin binds both fibrin(ogen) isoforms with similar high affinity (Kd values of about 0.5 μM) even though it does not interact with the γ'-chain. The batroxobin-binding sites on fibrin(ogen) only partially overlap with those of thrombin because thrombin attenuates, but does not abrogate, the interaction of γA/γA-fibrinogen with batroxobin. Furthermore, although both thrombin and batroxobin bind to the central E-region of fibrinogen with a Kd value of 2-5 μM, the α(17-51) and Bβ(1-42) regions bind thrombin but not batroxobin. Once bound to fibrin, the capacity of batroxobin to promote fibrin accretion is 18-fold greater than that of thrombin, a finding that may explain the microvascular thrombosis that complicates envenomation by B. atrox moojeni. Therefore, batroxobin binds fibrin(ogen) in a manner distinct from thrombin, which may contribute to its higher affinity interaction, selective fibrinopeptide A release, and prothrombotic properties.
authors.affiliation: Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada; Departments of Medical Sciences, Hamilton, Ontario L8L 2X2, Canada.
authors.forename: Trang T
authors.initials: TT
authors.lastname: Vu
authors.affiliation: Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada; Medicine, Hamilton, Ontario L8L 2X2, Canada.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Stafford
authors.affiliation: Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada; Medicine, Hamilton, Ontario L8L 2X2, Canada.
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Leslie
authors.affiliation: Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada; Medicine, Hamilton, Ontario L8L 2X2, Canada.
authors.forename: Paul Y
authors.initials: PY
authors.lastname: Kim
authors.affiliation: Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada; Medicine, Hamilton, Ontario L8L 2X2, Canada.
authors.forename: James C
authors.initials: JC
authors.lastname: Fredenburgh
authors.affiliation: Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada; Departments of Medical Sciences, Hamilton, Ontario L8L 2X2, Canada; Medicine, Hamilton, Ontario L8L 2X2, Canada; Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8L 2X2, Canada. Electronic address: weitzj@taari.ca.
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Weitz
mesh_terms: D000818:Animals; D012103:Batroxobin / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D005344:Fibrinopeptide A / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D013917:Thrombin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D005344:Fibrinopeptide A; D012103:Batroxobin; D013917:Thrombin
keywords: Batroxobin; Blood Coagulation Factors; Fibrin; Fibrinogen; Fibrinopeptides; Snake Venom; Thrombin