David, Charles N. and Easterbrook, Kenneth
FERRITIN IN THE FUNGUS PHYCOMYCES.
In: Journal of Cell Biology, Vol. 48: pp. 15-28
The iron-protein ferritin has been purified from mycelium, sporangiophores, and spores of
the fungus Phycomyces blakesleeanus. It has a protein-to-iron ratio of 5, a sedimentation coefficient
of 55S, a buoyant density in CsCI of 1 .82 g/cm3, and the characteristic morphology
of ferritin in the electron microscope . Apoferritin prepared from Phycomyces ferritin has a
sedimentation coefficient of 18S and consists of subunits of molecular weight 25,000 . In the
cytoplasm of Phycomyces, ferritin is located on the surface of lipid droplets (0 .5-2 .0 y in
diameter) where it forms crystalline monolayers which are conspicuous in electron micrographs
of sporangiophore thin-sections . Ferritin is found in all developmental stages of
Phycomyces but is concentrated in spores . The level of ferritin iron is regulated by the iron
level in the growth medium, a 50-fold increase occurring on iron-supplemented medium .