tailieunhanh - Báo cáo khoa học: Identification and characterization of novel salivary thrombin inhibitors from the ixodidae tick, Haemaphysalis longicornis

Novel antithrombin molecules were identified from the ixodidae tick, Haemaphysalis longicornis. These molecules, named madanin 1 and 2, are 7-kDa proteins and show no significant similarities to any previously identified proteins. Assays using human plasma showed that madanin 1 and 2 dose-dependently prolonged both activated partial throm-boplastin time and prothrombin time, indicating that they inhibit both the intrinsic and extrinsic pathways. Direct binding assay by surface plasmon resonance measurement demonstrated that madanin 1 and 2 specifically interacted with thrombin | Eur. J. Biochem. 270 1926-1934 2003 FEBS 2003 doi Identification and characterization of novel salivary thrombin inhibitors from the ixodidae tick Haemaphysalis longicornis Shiroh Iwanaga1 Masakazu Okada1 Haruhiko Isawa3 Akihiro Morita2 Masao Yuda2 and Yasuo Chinzei2 1Laboratory of Chemistry and Utilization of Animal Resources Faculty of Agriculture Kobe University Japan department of Medical Zoology School of Medicine Mie University Tsu Japan 3 Laboratory of Physiology and Biochemistry Department of Medical Entomology National Institute of Infectious Diseases Tokyo Japan Novel antithrombin molecules were identified from the ixodidae tick Haemaphysalis longicornis. These molecules named madanin 1 and 2 are 7-kDa proteins and show no significant similarities to any previously identified proteins. Assays using human plasma showed that madanin 1 and 2 dose-dependently prolonged both activated partial thromboplastin time and prothrombin time indicating that they inhibit both the intrinsic and extrinsic pathways. Direct binding assay by surface plasmon resonance measurement demonstrated that madanin 1 and 2 specifically interacted with thrombin. Furthermore it was clearly shown that madanin 1 and 2 inhibited conversion of fibrinogen into fibrin by thrombin thrombin-catalyzed activation of factor V and factor VIII and thrombin-induced aggregation of platelets without affecting thrombin amidolytic activity. These results suggest that madanin 1 and 2 bind to the anion-binding exosite 1 on the thrombin molecule but not to the active cleft and interfere with the association of fibrinogen factor V factor VIII and thrombin receptor on platelets with an anion-binding exosite 1. They appear to be exosite 1-directed competitive inhibitors. Keywords anticoagulant Haemaphysalis longicornis salivary gland thrombin inhibitor tick. Thrombin has various physiological functions and plays important roles in hemostasis. For example in the final step of .