Characteristics and expression of binding sites specific for ferritin H-chain on human cell lines.
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.
Institute of Internal Medicine, Milano, Italy.
S
S
Fargion
P
P
Arosio
A L
AL
Fracanzani
V
V
Cislaghi
S
S
Levi
A
A
Cozzi
A
A
Piperno
G
G
Fiorelli
D001665:Binding Sites; D002455:Cell Division; D002460:Cell Line; D055598:Chemical Phenomena; D002621:Chemistry; D005293:Ferritins / Q000145:classification / Q000378:metabolism*; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism / Q000473:pathology; D011994:Recombinant Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured
D011994:Recombinant Proteins; D005293:Ferritins