Diphtheria toxin fragment A interacts with Cibacron blue in solution, although it is not retained by blue Sepharose columns. Difference spectral titration of fragment A with the dye gives a dissociation constant of the order of 10−5 M and a 1:1 stoichiometry for the complex. In equilibrium dialysis experiments Cibacron blue behaves as a competitive inhibitor of the binding of NAD to diphtheria toxin fragment A. The dye inhibits in a non-competitive way the fragment A-catalysed transfer of ADP-ribose from NAD to elongation factor 2 (EF2). By affinity chromatography on blue Sepharose a binding of EF2 and of ADP-ribosyl-EF2 with the dye is also demonstrated. GDP, GTP and GDP(CH2)P are able to displace EF2 from blue Sepharose.
Interaction of diphtheria toxin fragment A and of elongation factor 2 with Cibacron blue
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Fioretta Rambelli, Maurizio Brigotti, Simonetta Sperti, Lucio Montanaro; Interaction of diphtheria toxin fragment A and of elongation factor 2 with Cibacron blue. Biosci Rep 1 September 1987; 7 (9): 737–743. doi: https://doi.org/10.1007/BF01116867
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