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  • Life and Medical Sciences  (2)
  • Russell's viper venom protease  (1)
  • cAMP phosphodiesterase  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Molecular changes during the activation of coagulation factor V by snake venom proteases (1983)
    Springer
    The protein journal 2 (1983), S. 171-185 
    Details
    ISSN: 1573-4943
    Keywords: blood coagulation factor V ; snake venoms ; thrombocytin ; Russell's viper venom protease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thrombin activation of factor V constitutes an important feedback reaction in the regulation of coagulation. We therefore examined the details of activation of bovine factor V by two purified snake venom proteolytic enzymes, factor V-activating protease from Russell's viper venom and a platelet-aggregating enzyme, thrombocytin, fromBothrops atrox venom. The reactions were followed by changes in factor V coagulant activity, immunoelectrophoresis, and electrophoresis of radiolabeled factor V in sodium dodecylsulfate under reducing conditions. When factor V (M r 330,000) was exposed to factor V-activating protease at an enzyme-to-substrate ratio of 1:35 at 37°, cleavage occurred in 1 min, with formation of an intermediate (M r 250,000) coincident with a nine-fold activity increase. By 2 min, additional cleavage occurred, with disappearance of the intermediate and formation of two final fragments (M r 150,000 and 100,000) but no further change in coagulant activity. The concentration of these components remained unchanged from 5 to 15 min. Immunoelectrophoresis against antiserum directed against factor V confirmed cleavage of the molecule. Incubation of factor V with thrombocytin at 37° for 1 min resulted in a four-fold increase of factor V activity, with the formation of an intermediate (M r 220,000). By 2 min, a 7.5-fold activation was found, with a decline in the concentration of the intermediate; the predominant species hasM r =130,000. At 5 min the intermediate disappeared and a second, final fragment ofM r of ∼150,000 appeared without further change in coagulant activity. Immunoelectrophoresis again confirmed selective proteolysis. Thus, incubation of factor V-activating protease or thrombocytin with factor V results in different molecular alterations associated with an increase in the coagulant activity of this clotting factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025352
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of iodopropyl derivatives of adenosine 3′,5′-cyclic-monophosphate: Potential affinity labels of cAMP binding sites in enzymes (1983)
    Springer
    The protein journal 2 (1983), S. 113-129 
    Details
    ISSN: 1573-4943
    Keywords: cyclic AMP derivatives ; affinity labels ; chemical modification of enzymes ; nucleotide affinity labels ; cAMP phosphodiesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The syntheses of two potential cAMP affinity lables, 1,N 6-(3-iodopropyleno)adenosine 3′,5′-cyclic-monophosphate and 2′-O-(2-iodo-3-hydroxypropyl) adenosine 3′,5′-cyclic-monophosphate, by a two-step chemical procedure are described. TheN 6- and 2′-O-allyl intermediates were prepared selectively by alkylation of cAMP in organic and alkaline aqueous solutions, respectively. Treatment of theN 6-allyl derivative withN-iodosuccinimide resulted in iodine addition to the double bond and cyclization to theN 1 position of the purine ring. The iodohydrin analog was synthesized by reaction of 2′-O-allyl-cAMP with potassium iodide and thallium trichloride in acetate buffered solution. The products were isolated by column chromatography and characterized by thin-layer chromatography, elemental analysis, and ultraviolet,13C, and1H NMR spectroscopy. The cAMP analogs were found to react with lysine and cysteine. Both cAMP derivatives were tested for their reaction with the low-K m cAMP phosphodiesterase of human platelets. The ribose-substituted analog functioned as a competitive inhibitor (K I =0.72 μM) and caused a time-dependent irreversible inactivation of the phosphodiesterase. In contrast, the purine-substituted derivative acted neither as a reversible competitive inhibitor nor as an irreversible inactivator of the enzyme. These results indicate the specificity of these potential cAMP analogs in their interaction with the phosphodiesterase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025376
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  • 3
    Electronic Resource
    Electronic Resource
    Inhibition of ADP-induced platelet activation by 7-chloro-4-nitrobenz-2-oxa-1,3-diazole: Covalent modification of aggregin, a putative ADP receptor (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 61 (1996), S. 97-108 
    Details
    ISSN: 0730-2312
    Keywords: aggregin ; chemical modification ; ADP-induced platelet responses ; NBD-Cl ; cAMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: ADP-induced platelet responses play an important role in the maintenance of hemostasis. There has been disagreement concerning the identity of an ADP receptor on the platelet surface. The chemical structure of 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl) shows considerable resemblance to that of the adenine moiety of adenine-based nucleotides. The reagent has been previously used by other investigators as an affinity label for adenine nucleotide-requiring enzymes, such as mitochondrial ATPase and the catalytic subunit of cAMP-dependent protein kinase. Since ADP-induced platelet responses depend on the binding of ADP to its receptor, we investigated the effect on ADP-induced platelet responses and the nature of ADP-binding protein modified by NBD-Cl. NBD-Cl inhibited ADP-induced shape change and aggregation of platelets in platelet-rich plasma in a concentration- and time-dependent manner. NBD-Cl also inhibited ADP-induced shape change, aggregation, exposure of fibrinogen binding sites, secretion, and calcium mobilization in washed platelets. NBD-Cl did not act as an agonist for platelet shape change and aggregation. Covalent modification of platelets by NBD-Cl blocked the ability of ADP to antagonize the increase in intracellular levels of cAMP mediated by iloprost (a stable analogue of prostaglandin I2). NBD-Cl was quite specific in inhibiting platelet aggregation by those agonists, e.g., ADP, collagen, and U44619 (a thromboxane mimetic), that completely or partially depend on the binding of ADP to its receptor. Autoradiogram of the gel obtained by SDS-PAGE of solubilized platelets modified by [14C]-NBD-Cl showed the presence of a predominant radiolabeled protein band at 100 kDa corresponding to aggregin, a putative ADP receptor. The intensity of this band was considerably decreased when platelets were either preincubated with ADP and ATP or covalently modified by a sulfhydryl group modifying reagent before modification by [14C]-NBD-Cl. These results (1) indicate that covalent modification of aggregin by NBD-Cl contributed to loss of the ADP-induced platelet responses, and (2) suggest that there is a sulfhydryl group in the ADP-binding domain of aggregin. © 1996 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Cellular and molecular regulation of factor V expression in human megakaryocytes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 153 (1992), S. 277-287 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The mechanisms responsible for regulating FV expression in normal human megakaryocytes are unknown. To test the hypothesis that they are related to cell maturation events, we correlated human megakaryocyte FV antigen content with several putative maturation markers including cell size, morphologic stage of development, and ploidy level. Mature megakaryocytes were isolated from normal marrow by counterflow centrifugal elutriation. The cells were immunofluorescently labeled with a monoclonal antibody probe (B10) directed against the FV connecting peptide (150 kDa) and then reacted with Chromomycin A3 to allow for simultaneous DNA quantitation in the same cell. After processing, individual cells were stages and sized. FV antigen and nuclear DNA levels (ploidy) were measured by microphotometric measurements of total cytoplasmic or nuclear fluorescence. A total of 1,006 cells were examined, of which 12% were stage I, 8% were stage II, 35% were stage III, and 45% were stage IV. The geometric mean diameter (± SD) of cells in these stages was 48.3 ± 11.8 μm2, 54.9 ± 14.4 μm2, 61.7 ± 20.02 μm2, and 56.7 ± 13.2 μm2, respectively. Respective ploidy values in arbitrary fluorescence units, where 2 N = 5%, were 28.2 ± 18.2%, 31.4 ± 19.3%, 54.3 ± 26.6%, and 33.2 ± 22.7%. Calculated correlation coefficients (r) and coefficient of determination (r2) values suggested that FV antigen levels varied independently of any of the maturation markers studied. However, FV antigen levels could be upregulated by 24 h exposure to 8 nM phorbol myristate acetate (PMA). Presence of FV mRNA in a pure population of megakaryocytes was demonstrated by in situ hybridization and the polymerase chain reaction. Relative levels of megakaryocyte FV mRNA, as assessed by in situ hybridization, failed to reveal a detectable change after PMA exposure in spite of an increase in detectable protein. These data suggest that FV synthesis may be regulated at the post-transcriptional level and that it is subject to regulatory influences which are not coordinately linked to development of other terminal maturation markers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041530207
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