A STUDY OF THE MECHANISM OF FERRITIN FORMATION - THE EFFECT OF PH, IONIC-STRENGTH AND TEMPERATURE, INHIBITION BY IMIDAZOLE AND KINETIC-ANALYSIS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 107  (2) , 447-453
Abstract
The rate of [horse] ferritin formation in the buffers 4-morpholinepropanesulfonic acid (Mops), 4-morpholineethanesulfonic acid (Mes) and imidazole at pH values from 5.0 to 6.5 is quite similar. The rate of Fe deposition is much greater in Mops and Mes at pH values above 6.5 than in imidazole. Increasing the concentration of imidazole inhibits ferritin formation and also leads to a transformation in the shape of the kinetic curves observed. This inhibition is also observed at constant ionic strength but is not found for non-complexing buffers such as Mops. An inhibition of ferritin formation in imidazole and in Mops buffers is also observed with increasing ionic strength. The unprotonated form of imidazole may inhibit Fe deposition, possibly by binding to the active site of the apoferritin molecule. The temperature dependence of Fe deposition was examined. An optimum temperature of 50.degree. C was found but the Arrhenius plots were non-linear. On the basis of these and previous results, a kinetic model is developed which accounts well for ferritin formation at pH values below 6.5 and above 7.0 in non-complexing buffers. The model does not account for the kinetics observed at pH values close to neutrality.

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