1. Mechanism of action of the antiplatelet peptide, arietin, from Bitis arietans venom
T F Huang, W J Wang, C M Teng, C Ouyang Biochim Biophys Acta. 1991 May 24;1074(1):144-50. doi: 10.1016/0304-4165(91)90053-j.
Arietin, an Arg-Gly-Asp containing peptide from venom of Bitis arietans, inhibited aggregation of platelets stimulated by a variety of agonists with a similar IC50, 1.3-2.7.10(-7) M. It blocked aggregation through the interference of fibrinogen binding to fibrinogen receptors on platelet surface. In this paper, we further demonstrated that arietin had no significant effect on the intracellular mobilization of Ca2+ in Quin2-AM-loaded platelets stimulated by thrombin. It inhibited 125I-fibrinogen binding to ADP-stimulated platelets in a competitive manner (IC50, 1.1.10(-7) M). 125I-arietin bound to unstimulated, ADP-stimulated and elastase-treated platelets in a saturable manner and its Kd values were estimated to be 3.4.10(-7), 3.4.10(-8) and 6.5.10(-8) M, respectively, while the corresponding binding sites were 46,904, 48,958 and 34,817 per platelet, respectively. Arg-Gly-Asp-Ser (RGDS) inhibited 125I-arietin binding to ADP-stimulated platelets in a competitive manner. RGD-containing peptides, including trigramin and rhodostomin, EDTA and monoclonal antibody, 7E3, raised against glycoprotein IIb-IIIa complex, inhibited 125I-arietin binding to ADP-stimulated platelets, indicating that the binding sites of arietin appear to be located at or near glycoprotein IIb-IIIa complex. In conclusion, arietin and other RGD-containing trigramin-like peptides preferentially bind to the fibrinogen receptors associated with glycoprotein IIb-IIIa complex of the activated platelets, thus leading to the blockade of fibrinogen binding to its receptors and subsequent aggregation. The presence of RGD of arietin is essential for the expression of its biological activity. Its binding sites are overlapped with those of trigramin, rhodostomin and the monoclonal antibody, 7E3.
2. Purification and characterization of an antiplatelet peptide, arietin, from Bitis arietans venom
T F Huang, W J Wang, C M Teng, C S Liu, C Ouyang Biochim Biophys Acta. 1991 May 24;1074(1):136-43. doi: 10.1016/0304-4165(91)90052-i.
By means of Fractogel TSK-50, CM-Sephadex C-50 column chromatography, gel filtrations on Sephadex G-75 and Sephacryl S-200 columns and reverse-phase HPLC, an antiplatelet peptide, arietin, was purified from venom of Bitis arietans. Arietin was shown to be an Arg-Gly-Asp-containing peptide with a NH2-terminus, Ser-Pro-Pro-Val-Cys-Gly-Asn-Lys- (Mr 8500). Arietin dose-dependently inhibited aggregation of human platelet suspension stimulated by ADP, thrombin, collagen and U46619 with IC50, 1.3-2.7.10(-7) M, while it had no effect on the initial shape changes and only slightly affected ATP release of platelets caused by thrombin and collagen. Arietin also blocked platelet aggregation in platelet-rich plasma and whole blood, and inhibited thrombin-induced clot retraction of platelet-rich plasma. Furthermore, arietin (6.5.10(-8) M) completely blocked the fibrinogen-induced aggregation of elastase-treated platelets, indicating that arietin interferes with the fibrinogen binding to fibrinogen receptors on platelet membranes. In conclusion, arietin, an Arg-Gly-Asp-containing peptide, inhibits platelet aggregation probably through the blockade of fibrinogen binding to the activated platelets.
3. Cicerin and arietin, novel chickpea peptides with different antifungal potencies
X Y Ye, T B Ng, P F Rao Peptides. 2002 May;23(5):817-22. doi: 10.1016/s0196-9781(02)00005-0.
Two antifungal peptides with novel N-terminal sequences, designated cicerin and arietin were isolated from seeds of the chickpea (Cicer arietinum), respectively. Both peptides were adsorbed on Affi-gel blue gel and CM-Sepharose and exhibited a molecular weight of approximately 8.2 and 5.6 kDa, respectively. Arietin was more strongly adsorbed on CM-Sepharose than cicerin and manifested a higher translation-inhibiting activity in a rabbit reticulocyte lysate system and a higher antifungal potency toward Mycosphaerella arachidicola, Fusarium oxysporum and Botrytis cinerea. Both were devoid of mitogenic and anti-HIV-1 reverse transcriptase activities.
