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S Fargion, P Arosio, AL Fracanzani, V Cislaghi, S Levi, A Cozzi, A Piperno and G Fiorelli
Institute of Internal Medicine, Milano, Italy.
Purified recombinant human ferritin composed solely of H subunit was
radiolabeled and incubated with proerythroleukemic K562 human cells. A
specific binding was detected, and it could be displaced only by ferritins,
natural or recombinant, containing large proportion of the H subunit. The
specific ferritin H-chain binding was saturable, and cells showed 17,000 to
23,000 binding sites per cell. The affinity constant measured at 37 degrees
C was of 3 x 10(8) M-1. Treatment with pronase eliminated the specific
binding. The binding sites were expressed in a high number during the
cellular exponential phase of growth and progressively decreased to
disappear when cells reached the plateau phase. Treatment of the cells with
desferrioxamine increased recombinant H-ferritin binding, while iron had
little effect. K562 cells induced to differentiate by hemin failed to bind
ferritin H. Ferritin H-chain binding capacity is present on various cell
lines such as HL60, lung cancer, and hepatoma cells. Analysis of the
binding sites by western blotting showed a peptide with apparent mol wt of
about 100 kd.
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| Copyright © 1988 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
