Lactoferrin binding sites and nuclear localization in K562(S) cells

Lactoterrin, a single chain cationic glycoprotein, present in the secondary granules of neutrophils, acts as a negative teed bark regulator of myelopoiesis. Specific receptors tor lactoferrin were detected on the surface ot different hematopoietic cell types. The influence of lactoferrin on cell growth in culture has been reported. Interactions of lactoferrin with DNA were also demonstrated. In the present paper we confirm the presence of lactoferrin specific binding sites on K562 cells and we estimate the number of binding sites and the dissociation constant. By Western blotting analysis performed on K562 lysates we find a band uf about 120 kUa responsible for specific binding of lactoferrin. We also show that lactoferrin, after binding at the cell surface, is internalized in a temperature dependent way and is immunologkally detectable as a DNA-linked protein in nuclearextracts.