Open AccessA Study of the Mechanism of Ferritin Formation
Author(s) -
PÂQUES Eric P.,
PÂQUES Antoinette,
CRICHTON Robert R.
Publication year - 1980
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1980.tb06050.x
Subject(s) - imidazole , chemistry , ionic strength , ferritin , arrhenius equation , kinetics , inorganic chemistry , metal , reaction rate constant , activation energy , stereochemistry , organic chemistry , aqueous solution , biochemistry , physics , quantum mechanics
The rate of ferritin formation in the buffers 4‐morpholinepropanesulphonic acid (Mops), 4‐morpholineethanesulphonic acid (Mes) and imidazole at pH values from 5.0 to 6.5 is quite similar. However, the rate of iron 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. We conclude that the unprotonated form of imidazole inhibits iron deposition, possibly by binding to the active site of the apoferritin molecule. The temperature dependence of iron deposition was examined. An optimum temperature of 50°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.