Triflavin, an antiplatelet Arg-Gly-Asp-containing peptide, is a specific antagonist of platelet membrane glycoprotein IIb-IIIa complex.
Triflavin, an antiplatelet peptide containing Arg-Gly-Asp, purified from Trimeresurus flavoviridis venom, inhibits aggregation of human platelets stimulated by a variety of agonists. It blocks aggregation through interference with fibrinogen binding to its specific receptor on the platelet surface membrane in a competitive manner, but it has no apparent effect on intracellular events, such as thromboxane B2 formation, phosphoinositides breakdown and intracellular Ca2+ mobilization of thrombin-activated platelets. In this study, we determined the complete sequence of triflavin, which is composed of a single polypeptide chain of 70 amino acids. Its sequence is rich in cysteine and contains Arg-Gly-Asp at residues 49-51 in the carboxy-terminal domain. Triflavin shows about 68% identity of amino acid sequence with trigramin, which is a specific antagonist of the fibrinogen receptor associated with glycoprotein IIb/IIIa complex. [125I]Triflavin binds to unstimulated and ADP-stimulated platelets in a saturable manner and its Kd values are estimated to be 76 and 74 nM, respectively; the corresponding numbers of binding sites are 31,029 and 34,863 per platelet, respectively. [125I]Triflavin binding is blocked by Gly-Arg-Gly-Asp-Ser in a competitive manner. EDTA, the Arg-Gly-Asp-containing peptides (including naturally occurring polypeptides, trigramin and rhodostomin), and monoclonal antibody, 7E3, raised against GP IIb/IIIa complex, inhibit [125I]triflavin binding to unstimulated and ADP-stimulated human platelets. In conclusion, triflavin specifically binds to fibrinogen receptor associated with GP IIb/IIIa complex and its binding site is located at or near GP IIb/IIIa complex, overlapping with those of 7E3 and another Arg-Gly-Asp-containing polypeptide, rhodostomin.(ABSTRACT TRUNCATED AT 250 WORDS)
Huang
T F
TF
Pharmacological Institute, College of Medicine, National Taiwan University, Taipei.
Sheu
J R
JR
Teng
C M
CM
Chen
S W
SW
Liu
C S
CS
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D001667:Binding, Competitive; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005340:Fibrinogen / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D010980:Platelet Membrane Glycoproteins; C054194:trigramin; C070025:triflavin; D005340:Fibrinogen