title: Characterization of an ideal amphipathic peptide as a procoagulant agent.
abstract: On the basis of previous evidence that amphipathic helical peptides accelerate Factor IXa activation of Factor X [Blostein, Rigby, Furie, Furie and Gilbert (2000) Biochemistry 39, 12000-12006], the present study was designed to assess the procoagulant activity of an IAP (ideal amphipathic peptide) of Lys(7)Leu(15) composition. The results show that IAP accelerates Factor X activation by Factor IXa in a concentration-dependent manner and accelerates thrombin generation by Factor Xa with a comparable peptide- and substrate-concentration-dependence. A scrambled helical peptide with the same amino acid composition as IAP, but with its amphipathicity abolished, eliminated most of the aforementioned effects. The Gla (gamma-carboxyglutamic acid)-rich domain of Factor X is required for IAP activity, suggesting that this peptide behaves as a phospholipid membrane. This hypothesis was confirmed, using fluorescence spectroscopy, by demonstrating direct binding between IAP and the Gla-rich domain of Factor X. In addition, the catalytic efficiencies of the tenase and prothrombinase enzymatic complexes, containing cofactors Factor VIIIa and Factor Va respectively, are enhanced by IAP. Finally, we show that IAP delays clot lysis in vitro. In summary, these observations demonstrate that IAP not only enhances essential procoagulant reactions required for fibrin generation, but also inhibits fibrinolysis, suggesting a potential role for IAP as a haemostatic agent.
authors.affiliation: Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Room E-156, SMDB-Jewish General Hospital, 3755 Côte Sainte Catherine Road, Montreal, Quebec, Canada.
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Ganopolsky
authors.forename: Sophie
authors.initials: S
authors.lastname: Charbonneau
authors.forename: Henry T
authors.initials: HT
authors.lastname: Peng
authors.forename: Pang N
authors.initials: PN
authors.lastname: Shek
authors.forename: Mark D
authors.initials: MD
authors.lastname: Blostein
mesh_terms: D000595:Amino Acid Sequence; D001777:Blood Coagulation / Q000502:physiology; D001779:Blood Coagulation Factors / Q000737:chemistry / Q000378:metabolism*; D003029:Coagulants / Q000737:chemistry* / Q000494:pharmacology*; D015949:Factor IXa / Q000378:metabolism; D005170:Factor X / Q000378:metabolism; D005342:Fibrinolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology*; D017434:Protein Structure, Tertiary
chemical_list: D001779:Blood Coagulation Factors; D003029:Coagulants; D010455:Peptides; C530076:ideal amphipathic peptide; D005170:Factor X; D015949:Factor IXa