Interaction of Cibacron blue F3G-A with yeast phosphofructokinase.

The binding of Cibacron blue F3G-A to yeast phosphofructokinase was investigated by means of ultracentrifugation. Four moles of Cibacron blue are tightly bound per subunit of phosphofructokinase (dissociation constant = 0.26 microM). This stoichiometry does not correspond to the stoichiometry of ATP binding to yeast phosphofructokinase (two moles of ATP per subunit). Moreover, 32 moles of the dye are bound per subunit of phosphofructokinase to a second class of binding sites with low affinity (dissociation constant = = 53 microM). The action of Cibacron blue on yeast phosphofructokinase cannot be explained completely in terms of its function as ATP analogue.